A respirator is a device designed to protect the wearer from inhaling hazardous atmospheres including lead, , gases and particulate matter such as dusts and airborne pathogens such as viruses. There are two main categories of respirators: the air-purifying respirator, in which respirable air is obtained by filtering a contaminated atmosphere, and the air-supplied respirator, in which an alternate supply of breathable air is delivered. Within each category, different techniques are employed to reduce or eliminate noxious airborne contaminants.
Air-purifying respirators range from relatively inexpensive, single-use, disposable face masks, known as filtering facepiece respirators, reusable models with replaceable cartridges called elastomeric respirators, to powered air-purifying respirators (PAPR), which use a pump or fan to constantly move air through a filter and supply purified air into a mask, helmet or hood.
Alexander von Humboldt introduced a primitive respirator in 1799 when he worked as a mining engineer in Prussia.
Julius Jeffreys first used the word "respirator" as a mask in 1836.
In 1848, the first US patent for an air-purifying respirator was granted to Lewis P. Haslett for his 'Haslett's Lung Protector,' which filtered dust from the air using one-way clapper valves and a filter made of moistened wool or a similar porosity substance. Hutson Hurd patented a cup-shaped mask in 1879 which became widespread in industrial use.
Inventors in Europe included John Stenhouse, a Scottish chemist, who investigated the power of charcoal in its various forms, to capture and hold large volumes of gas. He built one of the first respirators able to remove toxic gases from the air, paving the way for activated carbon to become the most widely used filter for respirators. Irish physicist John Tyndall took Stenhouse's mask, added a filter of cotton wool saturated with lime, glycerin, and charcoal, and in 1871 invented a 'fireman's respirator', a hood that filtered smoke and gas from air, which he exhibited at a meeting of the Royal Society in London in 1874. Also in 1874, Samuel Barton patented a device that 'permitted respiration in places where the atmosphere is charged with noxious gases, or vapors, smoke, or other impurities.'
In the 1890s, the German surgeon Johannes Mikulicz began using a "mundbinde" ("mouth bandage") of sterilized cloth as a barrier against microorganisms moving from him to his patients. Along with his surgical assistant Wilhelm Hübener, he adapted a chloroform mask with two layers of cotton mull. Experiments conducted by Hübener showed that the "mouth bandage" or "surgical mask" (German: Operationsmaske, as Hübener called it) blocked bacteria.Schlich T, Strasser BJ. Making the medical mask: surgery, bacteriology, and the control of infection (1870s–1920s). Medical History. 2022;66(2):116-134. doi:10.1017/mdh.2022.5
One reason is due to the fact that respirator manufacturers are not allowed to modify a respirator once it is certified by NIOSH. In one case, a jury ruled against 3M for a respirator that was initially approved for asbestos, but was quickly disapproved once OSHA permissible exposure limits for asbestos changed. Combined with testimony that the plaintiff rarely wore a respirator around asbestos, the lack of evidence, and the limitation of liability from static NIOSH approval, the case was overturned.
Nonetheless, the costs of litigation reduced the margins for respirators, which was blamed for supply shortages for N95 respirators for anticipated pandemics, like avian influenza, during the 2000s.
During the COVID-19 pandemic, people in the United States, and in a lot of countries in the world, were urged to make their own cloth masks due to the widespread shortage of commercial masks.
A full facepiece covers the mouth, nose and eyes and if sealed, is sealed round the perimeter of the face. Unsealed versions may be used when air is supplied at a rate which prevents ambient gas from reaching the nose or mouth during inhalation.
Respirators can have half-face forms that cover the bottom half of the face including the nose and mouth, and full-face forms that cover the entire face. Half-face respirators are only effective in environments where the contaminants are not toxic to the eyes or facial area.
An escape respirator may have no component that would normally be described as a mask, and may use a bite-grip mouthpiece and nose clip instead. Alternatively, an escape respirator could be a time-limited self-contained breathing apparatus.
For hazardous environments, like , atmosphere-supplying respirators, like SCBAs, should be used.
A wide range of industries use respirators including healthcare & pharmaceuticals, defense & public safety services (defense, firefighting & law enforcement), oil and gas industries, manufacturing (automotive, chemical, metal fabrication, food and beverage, wood working, paper and pulp), mining, construction, agriculture and forestry, cement production, power generation, painting, shipbuilding, and the textile industry.
Respirators require user training in order to provide proper protection.
According to the NIOSH Respirator Selection Logic, air-purifying respirators are recommended for concentrations of hazardous particulates or gases that are greater than the relevant occupational exposure limit but less than the immediately dangerous to life or health level and the manufacturer's maximum use concentration, subject to the respirator having a sufficient assigned protection factor. For substances hazardous to the eyes, a respirator equipped with a full facepiece, helmet, or hood is recommended. Air-purifying respirators are not effective during firefighting, in oxygen-deficient atmosphere, or in an unknown atmosphere; in these situations a self-contained breathing apparatus is recommended instead.
Mechanical filters remove contaminants from air in several ways: interception when particles following a line of flow in the airstream come within one radius of a fiber and adhere to it; impaction, when larger particles unable to follow the curving contours of the airstream are forced to embed in one of the fibers directly; this increases with diminishing fiber separation and higher air flow velocity; by diffusion, where gas molecules collide with the smallest particles, especially those below 100 nm in diameter, which are thereby impeded and delayed in their path through the filter, increasing the probability that particles will be stopped by either of the previous two mechanisms; and by using an electrostatic charge that attracts and holds particles on the filter surface.
There are many different filtration standards that vary by jurisdiction. In the United States, the National Institute for Occupational Safety and Health defines the categories of particulate filters according to their NIOSH air filtration rating. The most common of these are the N95 respirator, which filters at least 95% of airborne particles but is not resistant to oil.
Other categories filter 99% or 99.97% of particles, or have varying degrees of resistance to oil.
In the European Union, European standard EN 143 defines the 'P' classes of particle filters that can be attached to a face mask, while European standard EN 149 defines classes of "filtering half masks" or "filtering facepieces", usually called .
According to 3M, the filtering media in respirators made according to the following standards are similar to U.S. N95 or European FFP2 respirators, however, the construction of the respirators themselves, such as providing a proper seal to the face, varies considerably. (For example, US NIOSH-approved respirators never include earloops because they don't provide enough support to establish a reliable, airtight seal.) Standards for respirator filtration the Chinese KN95, Australian / New Zealand P2, Korean 1st Class also referred to as KF94, and Japanese DS.
If the concentration of harmful gases is IDLH, in workplaces covered by the Occupational Safety and Health Act the US Occupational Safety and Health Administration specifies the use of air-supplied respirators except when intended solely for escape during emergencies.OSHA standard 29 CFR 1910.134 "Respiratory Protection" NIOSH also discourages their use under such conditions.
The ideal assumption of all respirator users exceeding the APF is termed the zero control failure rate by NIOSH. The term control failure rate here refers to the number of respirator users, per 100 users, that fail to reach the APF. The risk of user error affecting the failure rate, and the studies quantifying it, was, according to NIOSH, akin to the study of contraception failure rates.
This is despite there being a "reasonable expectation, of both purchasers and users, that none of the users will receive less protection than the class APF (when the masks are properly selected, fit tested by the employer, and properly worn by the users)". NIOSH expands on the methods for measuring this error in Chapter 7 of the draft report.
With regards to the effectiveness of fit testing in general, others have said:
ANSI suggested additional contaminant monitoring by employers to allow for the use of DM and DFM respirators, when the mass median aerodynamic diameter of dusts in contaminated workplaces is such that DM and DFM respirators could work. However, NIOSH pointed out that the poor adherence to OSHA regulations on exposure-level monitoring by employers, as well as lack of expertise in interpreting the collected data, would likely result in more workers being put at risk. In addition, NIOSH pointed out that the ANSI recommendations would effectively mandate the use of expensive Part 11 HEPA filters under Part 11 regulations, due to lack of adherence to exposure-level monitoring rules.
However, some HOC implementations, notably MSHA's, have been criticized for allowing mining operators to skirt engineering control noncompliance by requiring miners to wear respirators instead if the permissible exposure limit (PEL) is exceeded, without work stoppages, breaking the hierarchy of engineering controls. Another concern was fraud related to the inability to scrutinize engineering controls, unlike NIOSH-approved respirators, like the N95, which can be fit tested by anyone, are subject to the scrutiny of NIOSH, and are and protected under US federal law. NIOSH also noted, in a 2002 video about tuberculosis respirator use, that "engineering controls, like negative pressure isolation rooms may not control the TB hazard completely. The use of respirators is necessary".
A U.S. Department of Labor study showed that in almost 40 thousand American enterprises, the requirements for the correct use of respirators are not always met. Experts note that in practice it is difficult to achieve elimination of occupational morbidity with the help of respirators:
Other opinions concern the change in performance of respirators in use compared to when fit testing, and compared to engineering control alternatives:
Complaints have been leveled at early LANL NIOSH fit test panels (which included primarily military personnel) as being unrepresentative of the broader American populace. However, later fit test panels, based on a NIOSH facial survey conducted in 2003, were able to reach 95% representation of working US population surveyed. Despite these developments, 42 CFR 84, the US regulation NIOSH follows for respirator approval, allows for respirators that don't follow the NIOSH fit test panel provided that: more than one facepiece size is provided, and no chemical cartridges are made available.§135, §198, and §205.
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Pesticide Educational Resources Collaborative (PERC) ( PDF ) |
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Institut de recherche Robert-Sauve en santé et en sécurité du travail (IRSST) ( (2025). 9782550374657, Institut de recherche Robert-Sauve en sante et en securite du travail (IRSST), Commission de la sante et de la securite du travail du Quebec. . ISBN 9782550374657 ;
2 edition: (2013). 9782550404033, Institut de recherche Robert-Sauve en sante et en securite du travail (IRSST), Commission de la santé et de la sécurité du travail du Québec. . ISBN 9782550404033 ;
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Institut de recherche Robert-Sauve en sante et en securite du travai (IRSST) ( Publication no.: UT-024; Research Project: 0099-9230.) |
Institut de recherche Robert-Sauve en sante et en securite du travai (IRSST) ( N° de publication : UT-024; Projet de recherche: 0099-9230.) |
Institut National de Recherche et de Sécurité (INRS) () |
Spitzenverband der gewerblichen Berufsgenossenschaften und der Unfallversicherungsträger der öffentlichen Hand (DGUV) ( PDF ) |
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The UK Nuclear Industry Good PracIndustry Radiological Protection Coordination Group (IRPCG) () |
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Instituto de Salud Publica de Chile (ISPCH) ( PDF ) |
Instituto Nacional de Seguridad, Salud y Salud en el Trabajo (INSST) () |
For standard filter classes used in respirators, see Mechanical filter (respirator)#Filtration standards.
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