document_title: Swine influenza

question_text: which animal is the carrier of the h1n1 virus

root

text: Swine influenza

text: Signs and symptoms[edit]

text: In swine, an influenza infection produces fever, lethargy, sneezing, coughing, difficulty breathing and decreased appetite.[7] In some cases the infection can cause abortion. Although mortality is usually low (around 1–4%),[2] the virus can produce weight loss and poor growth, causing economic loss to farmers.[7] Infected pigs can lose up to 12 pounds of body weight over a three- to four-week period.[7] Swine have receptors to which both avian and mammalian influenza viruses are able to bind to, which leads to the virus being able to evolve and mutate into different forms.[8] Influenza A is responsible for infecting swine, and was first identified in the summer of 1918.[8] Pigs have often been seen as "mixing vessels", which help to change and evolve strains of disease that are then passed on to other mammals, such as humans.[8]

tag: p

text: Humans[edit]

text: Direct transmission of a swine flu virus from pigs to humans is occasionally possible (zoonotic swine flu).[citation needed] In all, 50 cases are known to have occurred since the first report in medical literature in 1958, which have resulted in a total of six deaths.[10] Of these six people, one was pregnant, one had leukemia, one had Hodgkin's lymphoma and two were known to be previously healthy.[10] Despite these apparently low numbers of infections, the true rate of infection may be higher, since most cases only cause a very mild disease, and will probably never be reported or diagnosed.[10]

text: According to the Centers for Disease Control and Prevention (CDC), in humans the symptoms of the 2009 "swine flu" H1N1 virus are similar to those of influenza and of influenza-like illness in general. Symptoms include fever; cough, sore throat, watery eyes, body aches, shortness of breath, headache, weight loss, chills, sneezing, runny nose, coughing, dizziness, abdominal pain, lack of appetite and fatigue. The 2009 outbreak has shown an increased percentage of patients reporting diarrhea and vomiting as well. The 2009 H1N1 virus is not zoonotic swine flu, as it is not transmitted from pigs to humans, but from person to person through airborne droplets.[citation needed]

text: Because these symptoms are not specific to swine flu, a differential diagnosis of probable swine flu requires not only symptoms, but also a high likelihood of swine flu due to the person's recent and past medical history. For example, during the 2009 swine flu outbreak in the United States, the CDC advised physicians to "consider swine influenza infection in the differential diagnosis of patients with acute febrile respiratory illness who have either been in contact with persons with confirmed swine flu, or who were in one of the five U.S. states that have reported swine flu cases or in Mexico during the seven days preceding their illness onset."[12] A diagnosis of confirmed swine flu requires laboratory testing of a respiratory sample (a simple nose and throat swab).[12]

text: The most common cause of death is respiratory failure. Other causes of death are pneumonia (leading to sepsis),[13] high fever (leading to neurological problems), dehydration (from excessive vomiting and diarrhea), electrolyte imbalance and kidney failure.[14] Fatalities are more likely in young children and the elderly.

text: Virology[edit]

text: Transmission[edit]

text: Between pigs[edit]

text: Influenza is quite common in pigs, with about half of breeding pigs having been exposed to the virus in the US.[15] Antibodies to the virus are also common in pigs in other countries.[15]

text: The main route of transmission is through direct contact between infected and uninfected animals.[7] These close contacts are particularly common during animal transport. Intensive farming may also increase the risk of transmission, as the pigs are raised in very close proximity to each other.[16][17] The direct transfer of the virus probably occurs either by pigs touching noses, or through dried mucus. Airborne transmission through the aerosols produced by pigs coughing or sneezing are also an important means of infection.[7] The virus usually spreads quickly through a herd, infecting all the pigs within just a few days.[2] Transmission may also occur through wild animals, such as wild boar, which can spread the disease between farms.[18]

text: To humans[edit]

text: People who work with poultry and swine, especially those with intense exposures, are at increased risk of zoonotic infection with influenza virus endemic in these animals, and constitute a population of human hosts in which zoonosis and reassortment can co-occur.[19] Vaccination of these workers against influenza and surveillance for new influenza strains among this population may therefore be an important public health measure.[20] Transmission of influenza from swine to humans who work with swine was documented in a small surveillance study performed in 2004 at the University of Iowa.[21] This study, among others, forms the basis of a recommendation that people whose jobs involve handling poultry and swine be the focus of increased public health surveillance.[19] Other professions at particular risk of infection are veterinarians and meat processing workers, although the risk of infection for both of these groups is lower than that of farm workers.[22]

text: Interaction with avian H5N1 in pigs[edit]

text: Pigs are unusual as they can be infected with influenza strains that usually infect three different species: pigs, birds and humans.[23] This makes pigs a host where influenza viruses might exchange genes, producing new and dangerous strains.[23] Avian influenza virus H3N2 is endemic in pigs in China, and has been detected in pigs in Vietnam, increasing fears of the emergence of new variant strains.[24] H3N2 evolved from H2N2 by antigenic shift.[25] In August 2004, researchers in China found H5N1 in pigs.[26]

text: These H5N1 infections may be quite common; in a survey of 10 apparently healthy pigs housed near poultry farms in West Java, where avian flu had broken out, five of the pig samples contained the H5N1 virus. The Indonesian government has since found similar results in the same region. Additional tests of 150 pigs outside the area were negative.[27][28]

text: Structure[edit]

text: The influenza virion is roughly spherical. It is an enveloped virus; the outer layer is a lipid membrane which is taken from the host cell in which the virus multiplies. Inserted into the lipid membrane are "spikes", which are proteins—actually glycoproteins, because they consist of protein linked to sugars—known as HA (hemagglutinin) and NA (neuraminidase). These are the proteins that determine the subtype of influenza virus (A/H1N1, for example). The HA and NA are important in the immune response against the virus; antibodies (proteins made to combat infection) against these spikes may protect against infection. The NA protein is the target of the antiviral drugs Relenza and Tamiflu. Also embedded in the lipid membrane is the M2 protein, which is the target of the antiviral adamantanes amantadine and rimantadine.

text: Classification[edit]

text: Of the three genera of influenza viruses that cause human flu, two also cause influenza in pigs, with influenza A being common in pigs and influenza C being rare.[29] Influenza B has not been reported in pigs. Within influenza A and influenza C, the strains found in pigs and humans are largely distinct, although because of reassortment there have been transfers of genes among strains crossing swine, avian, and human species boundaries.

text: Influenza C[edit]

text: Influenza viruses infect both humans and pigs, but do not infect birds.[30] Transmission between pigs and humans have occurred in the past.[31] For example, influenza C caused small outbreaks of a mild form of influenza amongst children in Japan[32] and California.[32] Because of its limited host range and the lack of genetic diversity in influenza C, this form of influenza does not cause pandemics in humans.[33]

text: Influenza A[edit]

text: Swine influenza is caused by influenza A subtypes H1N1,[34] H1N2,[34] H2N3,[35] H3N1,[36] and H3N2.[34] In pigs, four influenza A virus subtypes (H1N1, H1N2, H3N2 and H7N9) are the most common strains worldwide.[7] In the United States, the H1N1 subtype was exclusively prevalent among swine populations before 1998; however, since late August 1998, H3N2 subtypes have been isolated from pigs. As of 2004, H3N2 virus isolates in US swine and turkey stocks were triple reassortants, containing genes from human (HA, NA, and PB1), swine (NS, NP, and M), and avian (PB2 and PA) lineages.[37] In August 2012, the Center for Disease Control and Prevention confirmed 145 human cases (113 in Indiana, 30 in Ohio, one in Hawaii and one in Illinois) of H3N2v since July 2012.[38] The death of a 61-year-old Madison County, Ohio woman is the first in the nation associated with a new swine flu strain. She contracted the illness after having contact with hogs at the Ross County Fair.[39]

text: Diagnosis[edit]

text: The CDC recommends real-time PCR as the method of choice for diagnosing H1N1.[40] The oral or nasal fluid collection and RNA virus preserving filter paper card is commercially available.[41] This method allows a specific diagnosis of novel influenza (H1N1) as opposed to seasonal influenza. Near-patient point-of-care tests are in development.[42]

text: Prevention[edit]

text: Prevention of swine influenza has three components: prevention in pigs, prevention of transmission to humans, and prevention of its spread among humans.

text: Swine[edit]

text: Methods of preventing the spread of influenza among swine include facility management, herd management, and vaccination (ATCvet code: QI09AA03 (WHO)). Because much of the illness and death associated with swine flu involves secondary infection by other pathogens, control strategies that rely on vaccination may be insufficient.

text: Control of swine influenza by vaccination has become more difficult in recent decades, as the evolution of the virus has resulted in inconsistent responses to traditional vaccines. Standard commercial swine flu vaccines are effective in controlling the infection when the virus strains match enough to have significant cross-protection, and custom (autogenous) vaccines made from the specific viruses isolated are created and used in the more difficult cases.[43][44] Present vaccination strategies for SIV control and prevention in swine farms typically include the use of one of several bivalent SIV vaccines commercially available in the United States. Of the 97 recent H3N2 isolates examined, only 41 isolates had strong serologic cross-reactions with antiserum to three commercial SIV vaccines. Since the protective ability of influenza vaccines depends primarily on the closeness of the match between the vaccine virus and the epidemic virus, the presence of nonreactive H3N2 SIV variants suggests current commercial vaccines might not effectively protect pigs from infection with a majority of H3N2 viruses.[10][45] The United States Department of Agriculture researchers say while pig vaccination keeps pigs from getting sick, it does not block infection or shedding of the virus.[46]

text: Facility management includes using disinfectants and ambient temperature to control viruses in the environment. They are unlikely to survive outside living cells for more than two weeks, except in cold (but above freezing) conditions, and are readily inactivated by disinfectants.[2] Herd management includes not adding pigs carrying influenza to herds that have not been exposed to the virus. The virus survives in healthy carrier pigs for up to three months, and can be recovered from them between outbreaks. Carrier pigs are usually responsible for the introduction of SIV into previously uninfected herds and countries, so new animals should be quarantined.[15] After an outbreak, as immunity in exposed pigs wanes, new outbreaks of the same strain can occur.[2]

text: Humans[edit]

text: Swine can be infected by both avian and human flu strains of influenza, and therefore are hosts where the antigenic shifts can occur that create new influenza strains.

text: The transmission from swine to humans is believed to occur mainly in swine farms, where farmers are in close contact with live pigs. Although strains of swine influenza are usually not able to infect humans, this may occasionally happen, so farmers and veterinarians are encouraged to use face masks when dealing with infected animals. The use of vaccines on swine to prevent their infection is a major method of limiting swine-to-human transmission. Risk factors that may contribute to swine-to-human transmission include smoking and, especially, not wearing gloves when working with sick animals, thereby increasing the likelihood of subsequent hand-to-eye, hand-to-nose or hand-to-mouth transmission.[47]

text: Influenza spreads between humans when infected people cough or sneeze, then other people breathe in the virus or touch something with the virus on it and then touch their own face.[48] "Avoid touching your eyes, nose or mouth. Germs spread this way."[49] Swine flu cannot be spread by pork products, since the virus is not transmitted through food.[48] The swine flu in humans is most contagious during the first five days of the illness, although some people, most commonly children, can remain contagious for up to ten days. Diagnosis can be made by sending a specimen, collected during the first five days, for analysis.[50]

text: Recommendations to prevent spread of the virus among humans include using standard infection control, which includes frequent washing of hands with soap and water or with alcohol-based hand sanitizers, especially after being out in public.[51] Chance of transmission is also reduced by disinfecting household surfaces, which can be done effectively with a diluted chlorine bleach solution.[52]

text: Experts agree hand-washing can help prevent viral infections, including ordinary and the swine flu infections. Also, avoiding touching one's eyes, nose or mouth with one's hands helps to prevent the flu.[49] Influenza can spread in coughs or sneezes, but an increasing body of evidence shows small droplets containing the virus can linger on tabletops, telephones and other surfaces and be transferred via the fingers to the eyes, nose or mouth. Alcohol-based gel or foam hand sanitizers work well to destroy viruses and bacteria. Anyone with flu-like symptoms, such as a sudden fever, cough or muscle aches, should stay away from work or public transportation, and should contact a doctor for advice.[53]

text: Social distancing, another tactic, is staying away from other people who might be infected, and can include avoiding large gatherings, spreading out a little at work, or perhaps staying home and lying low if an infection is spreading in a community. Public health and other responsible authorities have action plans which may request or require social distancing actions, depending on the severity of the outbreak.

text: Vaccination[edit]

text: Vaccines are available for different kinds of swine flu. The U.S. Food and Drug Administration (FDA) approved the new swine flu vaccine for use in the United States on September 15, 2009.[54] Studies by the National Institutes of Health show a single dose creates enough antibodies to protect against the virus within about 10 days.[55]

text: In the aftermath of the 2009 pandemic, several studies were conducted to see who received influenza vaccines. These studies show that whites are much more likely to be vaccinated for seasonal influenza and for the H1N1 strain than African Americans [56] This could be due to several factors. Historically, there has been mistrust of vaccines and of the medical community from African Americans. Many African Americans do not believe vaccines or doctors to be effective. This mistrust stems from the exploitation of the African American communities during studies like the Tuskegee study. Additionally, vaccines are typically administered in clinics, hospitals, or doctor’s offices. Many people of lower socioeconomic status are less likely to receive vaccinations because they do not have health insurance.

text: Surveillance[edit]

text: Although there is no formal national surveillance system in the United States to determine what viruses are circulating in pigs,[57] an informal surveillance network in the United States is part of a world surveillance network.[58]

text: Treatment[edit]

text: Swine[edit]

text: As swine influenza is rarely fatal to pigs, little treatment beyond rest and supportive care is required.[15] Instead, veterinary efforts are focused on preventing the spread of the virus throughout the farm, or to other farms.[7] Vaccination and animal management techniques are most important in these efforts. Antibiotics are also used to treat this disease, which although they have no effect against the influenza virus, do help prevent bacterial pneumonia and other secondary infections in influenza-weakened herds.[15]

text: Humans[edit]

text: If a person becomes sick with swine flu, antiviral drugs can make the illness milder and make the patient feel better faster. They may also prevent serious flu complications. For treatment, antiviral drugs work best if started soon after getting sick (within two days of symptoms). Beside antivirals, supportive care at home or in a hospital focuses on controlling fevers, relieving pain and maintaining fluid balance, as well as identifying and treating any secondary infections or other medical problems. The U.S. Centers for Disease Control and Prevention recommends the use of oseltamivir (Tamiflu) or zanamivir (Relenza) for the treatment and/or prevention of infection with swine influenza viruses; however, the majority of people infected with the virus make a full recovery without requiring medical attention or antiviral drugs.[59] The virus isolated in the 2009 outbreak have been found resistant to amantadine and rimantadine.[60]

text: In the U.S., on April 27, 2009, the FDA issued Emergency Use Authorizations to make available Relenza and Tamiflu antiviral drugs to treat the swine influenza virus in cases for which they are currently unapproved. The agency issued these EUAs to allow treatment of patients younger than the current approval allows and to allow the widespread distribution of the drugs, including by volunteers.[61]

text: History[edit]

text: Swine influenza was first proposed to be a disease related to human flu during the 1918 flu pandemic, when pigs became ill at the same time as humans.[62] The first identification of an influenza virus as a cause of disease in pigs occurred about ten years later, in 1930.[63] For the following 60 years, swine influenza strains were almost exclusively H1N1. Then, between 1997 and 2002, new strains of three different subtypes and five different genotypes emerged as causes of influenza among pigs in North America. In 1997–1998, H3N2 strains emerged. These strains, which include genes derived by reassortment from human, swine and avian viruses, have become a major cause of swine influenza in North America. Reassortment between H1N1 and H3N2 produced H1N2. In 1999 in Canada, a strain of H4N6 crossed the species barrier from birds to pigs, but was contained on a single farm.[63]

text: The H1N1 form of swine flu is one of the descendants of the strain that caused the 1918 flu pandemic.[64][65] As well as persisting in pigs, the descendants of the 1918 virus have also circulated in humans through the 20th century, contributing to the normal seasonal epidemics of influenza.[65] However, direct transmission from pigs to humans is rare, with only 12 recorded cases in the U.S. since 2005.[66] Nevertheless, the retention of influenza strains in pigs after these strains have disappeared from the human population might make pigs a reservoir where influenza viruses could persist, later emerging to reinfect humans once human immunity to these strains has waned.[67]

text: Swine flu has been reported numerous times as a zoonosis in humans, usually with limited distribution, rarely with a widespread distribution. Outbreaks in swine are common and cause significant economic losses in industry, primarily by causing stunting and extended time to market. For example, this disease costs the British meat industry about £65 million every year.[68]

text: 1918 pandemic[edit]

text: The 1918 flu pandemic in humans was associated with H1N1 and influenza appearing in pigs;[65] this may reflect a zoonosis either from swine to humans, or from humans to swine. Although it is not certain in which direction the virus was transferred, some evidence suggests, in this case, pigs caught the disease from humans.[62] For instance, swine influenza was only noted as a new disease of pigs in 1918, after the first large outbreaks of influenza amongst people.[62] Although a recent phylogenetic analysis of more recent strains of influenza in humans, birds, animals, and many others and swine suggests the 1918 outbreak in humans followed a reassortment event within a mammal,[69] the exact origin of the 1918 strain remains elusive.[70] It is estimated that anywhere from 50 to 100 million people were killed worldwide.[65][71]

text: 1976 U.S. outbreak[edit]

text: On February 5, 1976, a United States army recruit at Fort Dix said he felt tired and weak. He died the next day, and four of his fellow soldiers were later hospitalized. Two weeks after his death, health officials announced the cause of death was a new strain of swine flu. The strain, a variant of H1N1, is known as A/New Jersey/1976 (H1N1). It was detected only from January 19 to February 9 and did not spread beyond Fort Dix.[72]

text: This new strain appeared to be closely related to the strain involved in the 1918 flu pandemic. Moreover, the ensuing increased surveillance uncovered another strain in circulation in the U.S.: A/Victoria/75 (H3N2), which spread simultaneously, also caused illness, and persisted until March.[72] Alarmed public health officials decided action must be taken to head off another major pandemic, and urged President Gerald Ford that every person in the U.S. be vaccinated for the disease.[73]

text: The vaccination program was plagued by delays and public relations problems.[74] On October 1, 1976, immunizations began, and three senior citizens died soon after receiving their injections. This resulted in a media outcry that linked these deaths to the immunizations, despite the lack of any proof the vaccine was the cause. According to science writer Patrick Di Justo, however, by the time the truth was known—that the deaths were not proven to be related to the vaccine—it was too late. "The government had long feared mass panic about swine flu—now they feared mass panic about the swine flu vaccinations." This became a strong setback to the program.[75]

text: There were reports of Guillain–Barré syndrome (GBS), a paralyzing neuromuscular disorder, affecting some people who had received swine flu immunizations. Although whether a link exists is still not clear, this syndrome may be a side effect of influenza vaccines. As a result, Di Justo writes, "the public refused to trust a government-operated health program that killed old people and crippled young people." In total, 48,161,019 Americans, or just over 22% of the population, had been immunized by the time the National Influenza Immunization Program was effectively halted on December 16, 1976.[76] [77]

text: Overall, there were 1098 cases of GBS recorded nationwide by CDC surveillance, 532 of which occurred after vaccination and 543 before vaccination.[78] About one to two cases per 100,000 people of GBS occur every year, whether or not people have been vaccinated.[79] The vaccination program seems to have increased this normal risk of developing GBS by about to one extra case per 100,000 vaccinations.[79]

text: Recompensation charges were filed for over 4,000 cases of severe vaccination damage, including 25 deaths, totalling US$3.5 billion, by 1979.[80] The CDC stated most studies on modern influenza vaccines have seen no link with GBS,[79][81][82] Although one review gives an incidence of about one case per million vaccinations,[83] a large study in China, reported in the New England Journal of Medicine, covering close to 100 million doses of H1N1 flu vaccine, found only 11 cases of GBS, which is lower than the normal rate of the disease in China: "The risk-benefit ratio, which is what vaccines and everything in medicine is about, is overwhelmingly in favor of vaccination."[84]

text: 1988 U.S. outbreak[edit]

text: In September 1988, a swine flu virus killed one woman and infected others. A 32-year-old woman, Barbara Ann Wieners, was eight months pregnant when she and her husband, Ed, became ill after visiting the hog barn at a county fair in Walworth County, Wisconsin. Barbara died eight days later, after developing pneumonia.[85] The only pathogen identified was an H1N1 strain of swine influenza virus.[86] Doctors were able to induce labor and deliver a healthy daughter before she died. Her husband recovered from his symptoms.

text: Influenza-like illness (ILI) was reportedly widespread among the pigs exhibited at the fair. Of the 25 swine exhibitors aged 9 to 19 at the fair, 19 tested positive for antibodies to SIV, but no serious illnesses were seen. The virus was able to spread between people, since one to three health care personnel who had cared for the pregnant woman developed mild, influenza-like illnesses, and antibody tests suggested they had been infected with swine flu, but there was no community outbreak.[87][88]

text: In 1998, swine flu was found in pigs in four U.S. states. Within a year, it had spread through pig populations across the United States. Scientists found this virus had originated in pigs as a recombinant form of flu strains from birds and humans. This outbreak confirmed that pigs can serve as a crucible where novel influenza viruses emerge as a result of the reassortment of genes from different strains.[89][90][2] Genetic components of these 1998 triple-hybrid stains would later form six out of the eight viral gene segments in the 2009 flu outbreak.[91][92][93][94][95]

text: 2007 Philippine outbreak[edit]

text: On August 20, 2007, Department of Agriculture officers investigated the outbreak of swine flu in Nueva Ecija and central Luzon, Philippines. The mortality rate is less than 10% for swine flu, unless there are complications like hog cholera. On July 27, 2007, the Philippine National Meat Inspection Service (NMIS) raised a hog cholera "red alert" warning over Metro Manila and five regions of Luzon after the disease spread to backyard pig farms in Bulacan and Pampanga, even if these tested negative for the swine flu virus.[96][97]

text: 2009 Northern Ireland outbreak[edit]

text: Since November 2009, 14 deaths as a result of swine flu in Northern Ireland have been reported. The majority of the victims were reported to have pre-existing health conditions which had lowered their immunity. This closely corresponds to the 19 patients who had died in the year prior due to swine flu, where 18 of the 19 were determined to have lowered immune systems. Because of this, many mothers who have just given birth are strongly encouraged to get a flu shot because their immune systems are vulnerable. Also, studies have shown that people between the ages of 15 and 44 have the highest rate of infection. Although most people now recover, having any conditions that lower one's immune system increases the risk of having the flu become potentially lethal. In Northern Ireland now, approximately 56% of all people under 65 who are entitled to the vaccine have gotten the shot, and the outbreak is said to be under control.[98]

text: 2015 and 2017 India outbreaks[edit]

text: Swine flu outbreaks were reported in India in late 2014 and early 2015. As of March 19, 2015 the disease has affected 31,151 people and claimed over 1,841 lives.[6][99] The largest number of reported cases and deaths due to the disease occurred in the western part of India including states like Delhi, Madhya Pradesh, Rajasthan, and Gujarat. Researchers of MIT have claimed that the swine flu has mutated in India to a more virulent version with changes in Hemagglutinin protein. This has however been disputed by Indian researchers.[100]

text: There was another outbreak in India in 2017. The states of Maharashtra and Gujarat were the most affected states.[101] Gujarat high court has given Gujarat government instructions to control deaths by Swine Flu.[102] Actor Aamir Khan and wife Kiran Rao were among the latest to be afflicted by swine flu.[103] The couple spoke about their battle with the H1N1 virus via video conference at the Satyamev Jayate Water Cup event in Pune, which they had to skip due to ill-health. More than 1094 people died of Swine flu in India in year 2017 till 26 August 2017.[104]

text: 2015 Nepal outbreak[edit]

text: Swine flu outbreaks were reported in Nepal in the spring of 2015. As of April 21, 2015 the disease has claimed 26 lives in the most severely affected district, Jajarkot in Northwest Nepal.[105] Cases were also detected in the districts of Kathmandu, Morang, Kaski, and Chitwan.[106] As of 22 April 2015 the Nepal Ministry of Health reported that 2,498 people had been treated in Jajarkot, of whom 552 were believed to have swine flu, and acknowledged that the government's response had been inadequate.[107] The Jajarkot outbreak had just been declared an emergency when the April 2015 Nepal earthquake struck on 25 April 2015, diverting all medical and emergency resources to quake-related rescue and recovery.

text: 2016 Pakistan outbreak[edit]

text: There were seven cases of Swine flu reported in Punjab province of Pakistan mainly in the city of Multan in January 2017. Cases of Swine Flu have also been reported in Lahore & Faisalabad. [108]

text: 2017 Maldives outbreak[edit]

text: As of 16 March 2017, over a hundred confirmed cases of Swine flu and at least six deaths were reported in the Maldivian capital of Male' and some other islands. Makeshift flu clinics were opened in Male'.[109] Schools, universities and colleges in the capital were closed, prison visitations suspended, several events cancelled, and all non-essential travel to other islands outside the capital was advised against by the HPA. An influenza vaccination program focussed on pregnant women was initiated soon after.[110] An official visit by the Saudi King Salman bin Abdulaziz Al Saud to the Maldives during his Asian tour was also cancelled last minute amidst fears over the outbreak of swine flu.

text: H1N1 virus pandemic history[edit]

text: A study conducted in 2008, and published in the journal Nature, has managed to establish the evolutionary origin of the flu strain of swine origin (S-OIV).[111]

text: The phylogenetic origin of the flu virus that caused the 2009 pandemics can be traced before 1918. Around 1918, the ancestral virus, of avian origin, crossed the species boundaries and infected humans as human H1N1. The same phenomenon took place soon after in America, where the human virus was infecting pigs; it led to the emergence of the H1N1 swine strain, which later became the classic[clarification needed] swine flu.

text: New events of reassortment were not reported until 1968, when the avian strain H1N1 infected humans again; this time the virus met the strain H2N2, and the reassortment originated the strain H3N2. This strain has remained as a stable flu strain until now.

text: The mid-1970s were important for the evolution of flu strains. First, the re-emergence of the human H1N1 strain became a seasonal strain. Then, a small outbreak of swine H1N1 occurred in humans, and finally, the human H2N2 strain apparently became extinct. Around 1979, the avian H1N1 strain infected pigs and gave rise to Euroasiatic swine flu and H1N1 Euroasiatic swine virus, which is still being transmitted in swine populations.

text: The critical moment for the 2009 outbreak was between 1990 and 1993. A triple reassortment event in a pig host of North American H1N1 swine virus, the human H3N2 virus and avian H1N1 virus generated the swine H1N2 strain. Finally, the last step in S-OIV history was in 2009, when the virus H1N2 co-infected a human host at the same time as the Euroasiatic H1N1 swine strain. This led to the emergence of a new human H1N1 strain, which caused the 2009 pandemic.

text: On June 11, 2009, the World Health Organization raised the worldwide pandemic alert level to Phase 6 for swine flu, which is the highest alert level.[112] This alert level means that the swine flu had spread worldwide and there were cases of people with the virus in most countries. The pandemic level identifies the spread of the disease or virus and not necessarily the severity of the disease.

text: Swine flu spread very rapidly worldwide due to its high human-to-human transmission rate and due to the frequency of air travel.[112]

text: In 2015 the instances of swine flu substantially increased to five year highs with over 10,000 cases reported and 660 deaths in India.[113] The states reporting the highest number of cases and deaths are Rajasthan, Gujarat, Madhya Pradesh, Maharashtra, Delhi, and Telangana.[114] The circulating strain of influenza being the same, unmutant strain that caused global pandemic in 2009 (A H1N1 pdm 09), the sudden spurt of the cases in the beginning of 2015 left the Indian government unexplained but concerned. Government instructed the affected states to investigate into the epidemiological reasons of such spurt in the states, and had detailed the advisory guidelines to all states. The guidelines are mainly for (a) description of A H1N1 for prompt identification, detection, and distinction from the symptoms of other similar infection such as common flu(cold) (b) categorization of screening of influenza A H1N1 cases, (c) clinical management protocol of Pandemic influenza A H1N1, (d) providing home care, (e) collection of human sample.[115] Besides, through the National Centre for Diseases Control (NCDC), Directorate General of Health Services (DGHS), Government of India (GoI) had placed a tender to procure 8 kits of Assay sets, 37 kits of one step RT-PCR kit, and 36 kits of viral RNA extraction kits.[116]

text: Notes[edit]

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text: Further reading[edit]

text:
Alexander DJ (October 1982). "Ecological aspects of influenza A viruses in animals and their relationship to human influenza: a review". Journal of the Royal Society of Medicine. 75 (10): 799–811. PMC 1438138 . PMID 6752410.
Hampson AW, Mackenzie JS (November 2006). "The influenza viruses". The Medical Journal of Australia. 185 (10 Suppl): S39–43. PMID 17115950.
Lipatov AS, Govorkova EA, Webby RJ, et al. (September 2004). "Influenza: Emergence and Control". Journal of Virology. 78 (17): 8951–9. doi:10.1128/JVI.78.17.8951-8959.2004. PMC 506949 . PMID 15308692.
Van Reeth K (2007). "Avian and swine influenza viruses: our current understanding of the zoonotic risk". Veterinary Research. 38 (2): 243–60. doi:10.1051/vetres:2006062. PMID 17257572.
Webster RG, Bean WJ, Gorman OT, Chambers TM, Kawaoka Y (March 1992). "Evolution and ecology of influenza A viruses". Microbiological Reviews. 56 (1): 152–79. PMC 372859 . PMID 1579108.
Winkler WG (October 1970). "Influenza in animals: its possible public health significance". Journal of Wildlife Diseases. 6 (4): 239–42; discussion 247–8. doi:10.7589/0090-3558-6.4.239. PMID 16512120.

tag: ul


document_title: Smoke detector

question_text: which type of fire detector uses the effect of smoke on a light source and photo-electric cell

text: Smoke detector

text: History[edit]

text: The first automatic electric fire alarm was patented in 1890 by Francis Robbins Upton,[2] an associate of Thomas Edison.[3] George Andrew Darby patented the first European electrical heat detector in 1902 in Birmingham, England.[4] In the late 1930s Swiss physicist Walter Jaeger tried to invent a sensor for poison gas.[5] He expected that gas entering the sensor would bind to ionized air molecules and thereby alter an electric current in a circuit in the instrument.[5] His device did not meet its purpose: small concentrations of gas had no effect on the sensor's conductivity.[5] Frustrated, Jaeger lit a cigarette and was soon surprised to notice that a meter on the instrument had registered a drop in current.[6] Smoke particles from his cigarette had apparently done what poison gas could not.[6] Jaeger's experiment was one of the advances that paved the way for the modern smoke detector.[6] In 1939 Swiss physicist Ernst Meili devised an ionization chamber device capable of detecting combustible gases in mines.[7] He also invented a cold cathode tube that could amplify the small signal generated by the detection mechanism to a strength sufficient to activate an alarm.[7]

text: Ionization smoke detectors were first sold in the United States in 1951; they were used only in major commercial and industrial facilities in the next several years due to their large size and cost.[7] In 1955 simple home "fire detectors" for homes were developed,[8] detecting high temperatures.[9] The United States Atomic Energy Commission (USAEC) granted the first license to distribute smoke detectors using radioactive material in 1963.[5] The first low-cost smoke detector for domestic use was developed by Duane D. Pearsall in 1965, an individual replaceable battery-powered unit that could be easily installed.[10] The "SmokeGard 700"[11] was a beehive-shaped, strong fire-resistant steel unit.[12] The company began mass-producing these units in 1975.[6] Studies in the 1960s determined that smoke detectors respond to fires much faster than heat detectors.[9]

text: The first single-station smoke detector was invented in 1970 and made public the next year.[9] It was an ionization detector powered by a single 9-volt battery.[9] They cost about US$125 and sold at a rate of a few hundred thousand per year.[7] Several technological developments occurred between 1971 and 1976, including the replacement of cold-cathode tubes with solid-state electronics, which greatly reduced the detectors' sizes and made it possible to monitor battery life.[7] The previous alarm horns, which required specialty batteries, were replaced with horns that were more energy-efficient, enabling the use of commonly available batteries.[7] These detectors could also function with smaller amounts of radioactive source material, and the sensing chamber and smoke detector enclosure were redesigned for more effective operation.[7] The rechargeable batteries were often replaced by a pair of AA batteries along with a plastic shell encasing the detector. The 10-year-lithium-battery-powered smoke alarm was introduced in 1995.[9]

text: The photoelectric (optical) smoke detector was invented by Donald Steele and Robert Emmark of Electro Signal Lab and patented in 1972.[13]

text: Design[edit]

text: Ionization[edit]

text: An ionization smoke detector uses a radioisotope, typically americium-241, to ionize air; a difference due to smoke is detected and an alarm is generated. Ionization detectors are more sensitive to the flaming stage of fires than optical detectors, while optical detectors are more sensitive to fires in the early smouldering stage.[14]

text: The smoke detector has two ionization chambers, one open to the air, and a reference chamber which does not allow the entry of particles. The radioactive source emits alpha particles into both chambers, which ionizes some air molecules. There is a potential difference (voltage) between pairs of electrodes in the chambers; the electrical charge on the ions allows an electric current to flow. The currents in both chambers should be the same as they are equally affected by air pressure, temperature, and the ageing of the source. If any smoke particles enter the open chamber, some of the ions will attach to the particles and not be available to carry the current in that chamber. An electronic circuit detects that a current difference has developed between the open and sealed chambers, and sounds the alarm.[15] The circuitry also monitors the battery used to supply or back up power, and sounds an intermittent warning when it nears exhaustion. A user-operated test button simulates an imbalance between the ionization chambers, and sounds the alarm if and only if power supply, electronics, and alarm device are functional. The current draw of an ionization smoke detector is low enough for a small battery used as sole or backup power supply to be able to provide power for months or years without the need for external wiring.

text: Ionization smoke detectors are usually cheaper to manufacture than optical detectors. They may be more prone to false alarms triggered by non-hazardous events than photoelectric detectors,[16][17] and have been found to be much slower to respond to typical house fires.

text: Americium-241 is an alpha emitter with a half-life of 432.6 years.[18] Alpha particle radiation, as opposed to beta (electron) and gamma (electromagnetic) radiation, is used for two additional reasons: alpha particles have high ionization, so sufficient air particles will be ionized for the current to exist, and they have low penetrative power, meaning they will be stopped, safely, by the plastic of the smoke detector or the air. About one percent of the emitted radioactive energy of 241Am is gamma radiation. The amount of elemental americium-241 is small enough to be exempt from the regulations applied to larger sources. It includes about 37 kBq or 1 µCi of radioactive element americium-241 (241Am), corresponding to about 0.3 µg of the isotope.[19][20] This provides sufficient ion current to detect smoke, while producing a very low level of radiation outside the device.

text: The americium-241 in ionizing smoke detectors poses a potential environmental hazard, albeit a very small one. Disposal regulations and recommendations for smoke detectors vary from region to region.[21][22] The amount of radioactive material contained in ionizing smoke detectors is very small and thus doesn't represent a significant radiological hazard. If the americium is left in the ionization chamber of the alarm the radiological risk is insignificant because the chamber acts as a shield to the alpha radiation. A person would have to open the sealed chamber and ingest or inhale the americium for the risk to be significant. The radiation risk of exposure to an ionic smoke detector is much smaller than natural background radiation under normal operation.

text: Some European countries, like France,[23] and some US states and municipalities[24][unreliable source?] have banned the use of domestic ionic smoke alarms because of concerns that they are not reliable enough as compared other technologies.[25] Where an ionizing smoke detector has been the only detector, fires in the early stages have not always been effectively detected.

text: Photoelectric[edit]

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tag: table

text: A photoelectric, or optical smoke detector contains a source of infrared, visible, or ultraviolet light (typically an incandescent light bulb or light-emitting diode), a lens, and a photoelectric receiver (typically a photodiode). In spot-type detectors all of these components are arranged inside a chamber where air, which may contain smoke from a nearby fire, flows. In large open areas such as atria and auditoriums, optical beam or projected-beam smoke detectors are used instead of a chamber within the unit: a wall-mounted unit emits a beam of infrared or ultraviolet light which is either received and processed by a separate device, or reflected back to the receiver by a reflector. In some types, particularly optical beam types, the light emitted by the light source passes through the air being tested and reaches the photosensor. The received light intensity will be reduced due to scattering from particulates of smoke, air-borne dust, or other substances; the circuitry detects the light intensity and generates the alarm if it is below a specified threshold, potentially due to smoke.[26] In other types, typically chamber types, the light is not directed at the sensor, which is not illuminated in the absence of particles. If the air in the chamber contains particles (smoke or dust), the light is scattered and some of it reaches the sensor, triggering the alarm.[26]

text: According to the National Fire Protection Association (NFPA), "photoelectric smoke detection is generally more responsive to fires that begin with a long period of smoldering". Studies by Texas A&M and the NFPA cited by the City of Palo Alto California state, "Photoelectric alarms react slower to rapidly growing fires than ionization alarms, but laboratory and field tests have shown that photoelectric smoke alarms provide adequate warning for all types of fires and have been shown to be far less likely to be deactivated by occupants."

text: Although photoelectric alarms are highly effective at detecting smoldering fires and do provide adequate protection from flaming fires, fire safety experts and the National Fire Protection Agency recommend installing what are called combination alarms, which are alarms that either detect both heat and smoke, or use both the ionization and photoelectric processes. Some combination alarms may include a carbon monoxide detection capability.

text: The type and sensitivity of light source and photoelectric sensor, and type of smoke chamber differ between manufacturers.

text: Carbon monoxide and carbon dioxide detection[edit]

text: Carbon monoxide sensors detect potentially fatal concentrations of carbon monoxide gas, which may build up due to faulty ventilation where there are combustion appliances such as gas heaters and cookers, although there is no uncontrolled fire outside the appliance.[27]

text: High levels of carbon dioxide (CO2) may indicate a fire, and can be detected by a carbon dioxide sensor. Such sensors are often used to measure levels of CO2 which may be undesirable but not indicative of a fire; this type of sensor can also be used to detect and warn of the much higher levels generated by a fire. One manufacturer says that detectors based on CO2 levels are the fastest fire indicators, and also, unlike ionization and optical detectors, detect fires that do not generate smoke, such as those fuelled by alcohol or gasoline. CO2 fire detectors are not susceptible to false alarms due to particles, making them particularly suitable for use in dusty and dirty environments.[28]

text: Performance differences[edit]

text: A presentation by Siemens and the Canadian Fire Alarm Association reports the ionization detector as best at detecting incipient-stage fires with invisibly small particles, fast-flaming fires with smaller 0.01-0.4 micron particles, and dark or black smoke, while more modern photoelectric detectors are best at detecting slow-smouldering fires with larger 0.4–10.0 micron particles, and light-coloured white/grey smoke.[29]

text: Photoelectric smoke detectors respond faster to fire in its early, smouldering stage (before it breaks into flame). The smoke from the smouldering stage of a fire is typically made up of large combustion particles—between 0.3 and 10.0 µm. Ionization smoke detectors respond faster (typically 30–60 seconds) in the flaming stage of a fire. The smoke from the flaming stage of a fire is typically made up of microscopic combustion particles—between 0.01 and 0.3 µm. Also, ionization detectors are weaker in high air-flow environments, and because of this, the photoelectric smoke detector is more reliable for detecting smoke in both the smoldering and flaming stages of a fire.[30]

text: In June 2006, the Australasian Fire & Emergency Service Authorities Council, the peak representative body for all Australian and New Zealand fire departments, published an official report, 'Position on Smoke Alarms in Residential Accommodation'. Clause 3.0 states, "Ionization smoke alarms may not operate in time to alert occupants early enough to escape from smouldering fires."[31]

text: In August 2008, the International Association of Fire Fighters (IAFF, with over 300,000 members in North America) passed a resolution recommending the use of photoelectric smoke alarms, saying that changing to photoelectric alarms, "Will drastically reduce the loss of life among citizens and fire fighters."[32]

text: In May 2011, the Fire Protection Association of Australia's (FPAA) official position on smoke alarms stated, "Fire Prevention Association Australia considers that all residential buildings should be fitted with photoelectric smoke alarms..."[33]

text: In December 2011, the Volunteer Fire Fighter's Association of Australia published a World Fire Safety Foundation report, 'Ionization Smoke Alarms are DEADLY', citing research outlining substantial performance differences between ionization and photoelectric technology.[34]

text: In November 2013, the Ohio Fire Chiefs' Association (OFCA) published an official position paper supporting the use of photoelectric technology in Ohioan residences. The OFCA's position states, "In the interest of public safety and to protect the public from the deadly effects of smoke and fire, the Ohio Fire Chiefs' Association endorses the use of Photoelectric Smoke Alarms … In both new construction and when replacing old smoke alarms or purchasing new alarms, we recommend Photoelectric Smoke Alarms."[35]

text: In June 2014, tests by the North Eastern Ohio Fire Prevention Association (NEOFPA) on residential smoke alarms were broadcast on the ABC's 'Good Morning America' program. The NEOFPA tests showed ionization smoke alarms failing to activate in the early, smoldering stage of fire.[36] The combination ionization-photoelectric alarms failed to activate until an average of over 20 minutes after the stand-alone photoelectric smoke alarms. This vindicated the June 2006 official position of the Australasian Fire & Emergency Service Authorities Council (AFAC) and the October 2008, official position of the International Association of Fire Fighters (IAFF). Both AFAC and the IAFF recommend photoelectric smoke alarms, but not combination ionization/photoelectric smoke alarms.[37]

text: According to fire tests conformant to EN 54, the CO2 cloud from open fire can usually be detected before particulate.[28]

text: Due to the varying levels of detection capabilities between detector types, manufacturers have designed multi-criteria devices which cross-reference the separate signals to both rule out false alarms and improve response times to real fires.[30]

text: Obscuration is a unit of measurement that has become the standard way of specifying smoke detector sensitivity. Obscuration is the effect that smoke has on reducing sensor visibility, expressed in percent obscuration per unit length;[29] higher concentrations of smoke result in higher obscuration levels.

text:
Typical smoke detector obscuration ratings

Detector type
Obscuration

Ionization
2.6–5.0% obs/m (0.8–1.5% obs/ft)[26]

Photoelectric
0.70–13.0% obs/m (0.2–4.0% obs/ft)[26]

Aspirating
0.005–20.5% obs/m (0.0015–6.25% obs/ft)[26]

Laser
0.06–6.41% obs/m (0.02–2.0% obs/ft)[38]

text: Commercial[edit]

text: Commercial smoke detectors are either conventional or addressable, and are connected to security alarm or fire alarm systems controlled by fire alarm control panels (FACP).[39] These are the most common type of detector, and are usually significantly more expensive than single-station battery-operated residential smoke alarms.[39] They are used in most commercial and industrial facilities and other places such as ships and trains,[39] but are also part of some security alarm systems in homes.[40] These detectors don't need to have built in alarms, as alarm systems can be controlled by the connected FACP, which will set off relevant alarms, and can also implement complex functions such as a staged evacuation.[39]

text: Conventional[edit]

text: The word "conventional" is slang used to distinguish the method used to communicate with the control unit in newer addressable systems.[39] So called "conventional detectors" are smoke detectors used in older interconnected systems and resemble electrical switches by their way of working.[39] These detectors are connected in parallel to the signaling path so that the current flow is monitored to indicate a closure of the circuit path by any connected detector when smoke or other similar environmental stimulus sufficiently influences any detector.[39] The resulting increase in current flow (or a dead short) is interpreted and processed by the control unit as a confirmation of the presence of smoke and a fire alarm signal is generated.[39] In a conventional system, smoke detectors are typically wired together in each zone and a single fire alarm control panel usually monitors a number of zones which can be arranged to correspond to different areas of a building.[39] In the event of a fire, the control panel is able to identify which zone or zones contain the detector or detectors in alarm, but can not identify which individual detector or detectors are in a state of alarm.[39]

text: Addressable[edit]

text: An addressable system gives each detector an individual number, or address.[39] Addressable systems allow the exact location of an alarm to be plotted on the FACP, while allowing several detectors to be connected to the same zone.[39] In certain systems, a graphical representation of the building is provided on the screen of the FACP which shows the locations of all of the detectors in the building,[39] while in others the address and location of the detector or detectors in alarm are simply indicated.[39]

text: Addressable systems are usually more expensive than conventional non-addressable systems,[41] and offer extra options, including a custom level of sensitivity (sometimes called Day/Night mode) which can determine the amount of smoke in a given area and contamination detection from the FACP that allows determination of a wide range of faults in detection capabilities of smoke detectors.[39] Detectors become contaminated usually as a result of the build up of atmospheric particulates in the detectors being circulated by the heating and air-conditioning systems in buildings. Other causes include carpentry, sanding, painting, and smoke in the event of a fire.[42] Panels can also be interconnected to monitor a very large number of detectors in multiple buildings.[39] This is most commonly used in hospitals, universities, resorts and other large centres or institutions.[39]

text: Residential[edit]

text: Smaller, less expensive, smoke alarm systems, typically used in a domestic/residential environment, may be individual standalone units, or interconnected. They typically generate a loud acoustic warning signal as their only action. Several detectors (whether standalone or interconnected) are normally used in the rooms of a dwelling. There are inexpensive smoke alarms that may be interconnected so that any detector that triggers sounds all alarms. They are powered by mains electricity, with disposable or rechargeable battery backup. They may be interconnected by wires, or wirelessly.They are required in new installations in some jurisdictions.[43]

text: Several smoke detection methods are used and documented in industry specifications published by Underwriters Laboratories.[44] Alerting methods include:

text:
Audible tones

Usually around 3200 Hz due to component constraints (Audio advancements for persons with hearing impairments have been made)
85 dBA loudness at 10 feet

Spoken voice alert
Visual strobe lights

177 candela output

Tactile stimulation (e.g. bed or pillow shaker), although no standards existed as of 2008 for tactile stimulation alarm devices.

text: Some models have a hush or temporary silence feature that allows silencing, typically by pressing a button on the housing, without removing the battery. This is especially useful in locations where false alarms can be relatively common (e.g. near a kitchen), or users might remove the battery permanently to avoid the annoyance of false alarms, preventing the alarm from detecting a fire should one break out.

text: While current technology is very effective at detecting smoke and fire conditions, the deaf and hard of hearing community has raised concerns about the effectiveness of the alerting function in awakening sleeping individuals in certain high-risk groups such as the elderly, those with hearing loss and those who are intoxicated.[45] Between 2005 and 2007 research sponsored by the United States' National Fire Protection Association (NFPA) focused on understanding the cause of the higher number of deaths in such high-risk groups. Initial research into the effectiveness of the various alerting methods is sparse. Research findings suggest that a low frequency (520 Hz) square wave output is significantly more effective at awakening high risk individuals. Wireless smoke and carbon monoxide detectors linked to alert mechanisms such as vibrating pillow pads for the hearing impaired, strobes, and remote warning handsets are more effective at waking people with serious hearing loss than other alarms.[46]

text: Batteries[edit]

text: Batteries are used either as sole or as backup power for residential smoke detectors. Mains-operated detectors have disposable or rechargeable batteries; others run only on 9-volt disposable batteries. When the battery is exhausted a battery-only smoke detector becomes inactive; most smoke detectors chirp repeatedly if the battery is low. It has been found that battery-powered smoke detectors in many houses have dead batteries. It has been estimated[when?] that in the UK over 30% of smoke alarms may have dead or removed batteries. In response public information campaigns have been created to remind people to change smoke detector batteries regularly. In Australia, for example, a public information campaign suggests that smoke alarm batteries should be replaced on April Fools' Day every year.[47] In regions using daylight saving time, campaigns may suggest that people change their batteries when they change their clocks or on a birthday.

text: Some mains-powered detectors are fitted with a non-rechargeable lithium battery for backup with a life of typically ten years, after which it is recommended that the detector be replaced. User-replaceable disposable 9-volt lithium batteries, which last at least twice as long as alkaline batteries are available.

text: The US National Fire Protection Association recommends that home-owners replace smoke detector batteries with a new battery at least once per year, when it starts chirping (a signal that the battery is low), or when it fails a test, which the NFPA recommends to be carried out at least once per month by pressing the "test" button on the alarm.[48]

text: Reliability[edit]

text: A 2004 NIST report concluded that "Smoke alarms of either the ionization type or the photoelectric type consistently provided time for occupants to escape from most residential fires," and, "Consistent with prior findings, ionization type alarms provided somewhat better response to flaming fires than photoelectric alarms (57 to 62 seconds faster response), and photoelectric alarms provided (often) considerably faster response to smoldering fires than ionization type alarms (47 to 53 minutes faster response)."[17]

text: Regular cleaning can prevent false alarms caused by the build-up of dust and insects, particularly on optical type alarms as they are more susceptible to these factors. A vacuum cleaner can be used to clean domestic smoke detectors to remove detrimental dust. Optical detectors are less susceptible to false alarms in locations such as near a kitchen producing cooking fumes.[49]

text: On the night of May 31, 2001, Bill Hackert and his daughter Christine of Rotterdam, New York died when their house caught fire and a First Alert ionization smoke detector failed to sound.[50] The cause of the fire was a frayed electrical cord behind a couch that smoldered for hours before engulfing the house with flames and smoke.[50] The ionization smoke detector was found to be defectively designed, and in 2006 a jury in the United States District Court for the Northern District of New York decided that First Alert and its then parent company, BRK Brands, was liable for millions of dollars in damages.[50]

text: Installation and placement[edit]

text: In the United States most state and local laws regarding the required number and placement of smoke detectors are based upon standards established in NFPA 72, National Fire Alarm and Signaling Code.[51] Laws governing the installation of smoke detectors vary depending on the locality. However, some rules and guidelines for existing homes are relatively consistent throughout the developed world. For example, Canada and Australia require a building to have a working smoke detector on every level. The United States NFPA code cited in the previous paragraph requires smoke detectors on every habitable level and within the vicinity of all bedrooms. Habitable levels include attics that are tall enough to allow access.[51] Many other countries have comparable requirements.

text: In new construction, minimum requirements are typically more stringent. All smoke detectors must be hooked directly to the electrical wiring, be interconnected and have a battery backup. In addition, smoke detectors are required either inside or outside every bedroom, depending on local codes. Smoke detectors on the outside will detect fires more quickly, assuming the fire does not begin in the bedroom, but the sound of the alarm will be reduced and may not wake some people. Some areas also require smoke detectors in stairways, main hallways and garages.[52]

text: A dozen or more detectors may be connected via wiring or wirelessly such that if one detects smoke, the alarms will sound on all the detectors in the network, improving the likelihood that occupants will be alerted even if smoke is detected far from their location. Wired interconnection are more practical in new construction than for existing buildings.

text: In the UK the installation of smoke alarms in new builds must comply with British Standard BS5839 pt6. BS 5839: Pt.6: 2004 recommends that a new-build property consisting of no more than 3 floors (less than 200 square metres per floor) should be fitted with a Grade D, LD2 system. Building Regulations in England, Wales and Scotland recommend that BS 5839: Pt.6 should be followed, but as a minimum a Grade D, LD3 system should be installed. Building Regulations in Northern Ireland require a Grade D, LD2 system to be installed, with smoke alarms fitted in the escape routes and the main living room and a heat alarm in the kitchen; this standard also requires all detectors to have a mains supply and a battery back up.[53]

text: Standards[edit]

text: EN54 European standards[edit]

text: Fire detection products have the European Standard EN 54 Fire Detection and Fire Alarm Systems that is a mandatory standard for every product that is going to be delivered and installed in any country in the European Union (EU). EN 54 part 7 is the standard for smoke detectors. European standard are developed to allow free movement of goods in the European Union countries. EN 54 is widely recognized around the world. The EN 54 certification of each device must be issued annually.[54] [55]

text: Coverage of smoke and temperature detectors with European standard EN54[edit]

text:
Surface area (square metres)
Type of detector
Height (m)
Ceiling slope ≤20°
Ceiling slope >20°

Smax(square metres)
Rmax (m)
Smax (square metres)
Rmax(m)

SA ≤80
EN54-7
≤12
80
6,6
80
8,2

SA >80
EN54-7
≤6
60
5,7
90
8,7

6< h ≤ 12
80
6,6
110
9,6

SA ≤30
EN54-5 Clase A1
≤7,5
30
4,4
30
5,7

EN54-5 Clase A2,B,C,D,F,G
≤ 6
30
4,4
30
5,7

SA >30
EN54-5 Clase A1
≤7,5
20
3,5
40
6,5

EN54-5 Clase A2,B,C,D,E,F,G
≤6
20
3,5
40
6,5

text:
EN54-7: Smoke detector
EN54-5: Temperature detector
SA: Surface area
Smax (square metres): Maximum surface coverage
Rmax (m): Maximum radio

text: Information in "bold" is the standard coverage of the detector. Smoke detector coverage is 60 square metres and temperature smoke detector coverage is 20 square metres. Height from ground is an important issue for a correct protection.[56]

text: Australia and United States[edit]

text: In the United States, the first standard for home smoke alarms, NFPA 74, was established in 1967.[9] In 1969, the AEC allowed homeowners to use smoke detectors without a license.[5] The Life Safety Code (NFPA 101), passed by the National Fire Protection Association in 1976, first required smoke alarms in homes.[9] Smoke alarm sensitivity requirements in UL 217 were modified in 1985 to reduce susceptibility to nuisance alarms.[9] In 1988 BOCA, ICBO, and SBCCI model building codes begin requiring smoke alarms to be interconnected and located in all sleeping rooms.[9] In 1989 NFPA 74 first required smoke alarms to be interconnected in every new home construction, and in 1993 NFPA 72 first required that smoke alarms be placed in all bedrooms.[9] NFPA began requiring the replacement of smoke detectors after ten years in 1999.[9] In 1999 Underwriters Laboratory changed smoke alarm labeling requirements so that all smoke alarms must have a manufactured date written in Plain English.

text: In June 2013 a World Fire Safety Foundation report titled, 'Can Australian and U.S. Smoke Alarm Standards be Trusted?' was published in the official magazine of the Australian Volunteer Fire Fighter's Association. The report brings into question the validity of testing criteria used by American and Australian government agencies when undergoing scientific testing of ionization smoke alarms in smoldering fires.[57]

text: Legislation[edit]

text: In June 2010 the City of Albany, California enacted photoelectric-only legislation after a unanimous decision by the Albany City Council; several other Californian and Ohioan cities enacted similar legislation shortly afterwards.[58]

text: In November 2011 the Northern Territory enacted Australia's first residential photoelectric legislation mandating the use of photoelectric smoke alarms in all new Northern Territory homes.[59]

text: In the Australian State of Queensland, from 1 January 2017 all smoke alarms in new dwellings (or where a dwelling is substantially renovated) must be photoelectric, not also contain an ionisation sensor, be hardwired to the mains power supply with a secondary power source (i.e. battery) and be interconnected with every other smoke alarm in the dwelling so all activate together. From that date, all replacement smoke alarms must be photoelectric.

text: From 1 January 2022, all dwellings sold, leased or where a lease is renewed must comply as for new dwellings.

text: From 1 January 2027, all dwellings must comply as for new dwellings.[60]

text: In June 2013, in an Australian Parliamentary speech, the question was asked, "Are ionization smoke alarms defective?" This was further to the Australian Government's scientific testing agency (the Commonwealth Scientific and Industrial Research Organisation - CSIRO) data revealing serious performance problems with ionization technology in the early, smoldering stage of fire, a rise in litigation involving ionization smoke alarms, and increasing legislation mandating the installation of photoelectric smoke alarms. The speech cited a May 2013, World Fire Safety Foundation report published in the Australian Volunteer Fire Fighter Association's magazine titled, 'Can Australian and U.S. Smoke Alarm Standards be Trusted?' The speech concluded with a request for one of the world's largest ionization smoke alarm manufacturers and the CSIRO to disclose the level of visible smoke required to trigger the manufacturers' ionization smoke alarms under CSIRO scientific testing.[61] The US state of California banned the sale of smoke detectors with replaceable batteries [62]