A respirator is type of mask designed to protect the wearer from inhaling hazardous atmospheres including lead fumes, vapors, 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.
thumb|A half-face [[elastomeric respirator|elastomeric air-purifying respirator. This kind of respirator is reusable, with the filters being replaced periodically.]]
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.
History
Earliest records to 19th century
thumb|upright|[[Plague doctor]]
The history of protective respiratory equipment can be traced back as far as the first century, when Pliny the Elder (–79) described using animal bladder skins to protect workers in Roman mines from red lead oxide dust. In the 16th century, Leonardo da Vinci suggested that a finely woven cloth dipped in water could protect sailors from a toxic weapon made of powder that he had designed.
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.
thumb|left|Woodcut of Stenhouse's mask
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 porous 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 charcoal 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.
20th century
thumb|right| "How a Man may Breathe Safely in a Poisonous Atmosphere", an apparatus providing oxygen while using caustic soda to absorb carbon dioxide, 1909
World War I
United States
In the 1970s, the successor to the United States Bureau of Mines and NIOSH developed standards for single-use respirators, and the first single-use respirator was developed by 3M and approved in 1972. 3M used a melt blowing process that it had developed decades prior and used in products such as ready-made ribbon bows and bra cups; its use in a wide array of products had been pioneered by designer Sara Little Turnbull.
1990s
21st century
==== Continuing mesothelioma litigation ==== <!-- Excerpted in N95 respirator article -->
thumb|right|upright=0.5|[[30 CFR 11 label, with asbestos approval]]
NIOSH certifies B Readers, people qualified to testify or provide evidence in mesothelioma personal injury lawsuits, in addition to regulating respirators. However, since 2000, the increasing scope of claims related to mesothelioma started to include respirator manufacturers to the tune of 325,000 cases, despite the primary use of respirators being to prevent asbestos and silica-related diseases. Most of these cases were not successful, or reached settlements of around $1000 per litigant, well below the cost of mesothelioma treatment.
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.
2024
Summary of modern respirators
<!-- target for redirect Full facepiece -->
thumb|Types of respirators by physical form.
All respirators have some type of facepiece held to the wearer's head with straps, a cloth harness, or some other method. Facepieces come in many different styles and sizes to accommodate all types of face shapes.
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 confined spaces, 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.
Use
User seal check
thumb|Multiple people doing positive pressure user seal checks.
Each time a wearer dons a respirator, they must perform a seal check to be sure that they have an airtight seal to the face so that air does not leak around the edges of the respirator. (PAPR respirators may not require this because they don't necessarily seal to the face.) This check is different than the periodic fit test that is performed using testing equipment. Filtering facepiece respirators are typically checked by cupping the hands over the facepiece while exhaling (positive pressure check) or inhaling (negative pressure check) and observing any air leakage around the facepiece. Elastomeric respirators are checked in a similar manner, except the wearer blocks the airways through the inlet valves (negative pressure check) or exhalation valves (positive pressure check) while observing the flexing of the respirator or air leakage. Manufacturers have different methods for performing seal checks and wearers should consult the specific instructions for the model of respirator they are wearing. Some models of respirators or filter cartridges have special buttons or other mechanisms built into them to facilitate seal checks.
Fit testing
Contrast with surgical mask
Surgical N95
thumb|left|upright=0.9|A [[3M 1860 surgical N95, with a non-surgical 3M 8210 in the background]]
== Respirator selection ==<!-- This section is linked from Personal protective equipment EDIT: section title renamed-->
Air-purifying respirators are respirators that draw in the surrounding air and purify it before it is breathed (unlike air-supplying respirators, which are sealed systems, with no air intake, like those used underwater). Air-purifying respirators filter particulates, gases, and vapors from the air, and may be negative-pressure respirators driven by the wearer's inhalation and exhalation, or positive-pressure units such as powered air-purifying respirators (PAPRs).
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.
Types of filtration
Mechanical filter
: Main Article: Mechanical filter respirator (and regulatory ratings) <!-- So don't put 'N95' here! -->
thumb|A video describing N95 certification testing
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 FFP masks.
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.
Canister or chemical cartridge
thumb|Combined gas and particulate [[gas mask canister, type BKF (БКФ), for protection against acid gases. It has a transparent body and a special sorbent that changes color upon saturation. This color change may be used for timely replacement of respirators' filters (like an end-of-service-life indicator, ESLI).|alt=]]
Chemical cartridges and gas mask canisters remove gases, volatile organic compounds (VOCs), and other vapors from breathing air by adsorption, absorption, or chemisorption. A typical organic vapor respirator cartridge is a metal or plastic case containing from 25 to 40 grams of sorption media such as activated charcoal or certain resins. The service life of the cartridge varies based, among other variables, on the carbon weight and molecular weight of the vapor and the cartridge media, the concentration of vapor in the atmosphere, the relative humidity of the atmosphere, and the breathing rate of the respirator wearer. When filter cartridges become saturated or particulate accumulation within them begins to restrict air flow, they must be changed.
If the concentration of harmful gases is immediately dangerous to life or health, 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. NIOSH also discourages their use under such conditions.
Air-purifying respirators
Filtering facepiece
thumb|Filtering facepiece half mask with exhalation valve (class: FFP3)|alt=A white cup-type filtering facepiece respirator with an exhalation valve and red head and neck straps|left
Elastomeric
thumb|[[New York Police Department officer wearing a 3M elastomeric respirator with P100-standard particulate filters in the aftermath of the 2007 New York City steam explosion|alt=Head-only portrait of a male police officer wearing a navy blue peaked cap emblazoned with the New York City coat of arms and navy uniform shirt with gold collar insignia identifying him as a member of the 112th Precinct. His nose and mouth are covered by a gray rubber respirator with bright pink filters.]]
Powered air-purifying respirators
Atmosphere-supplying respirators
These respirators do not purify the ambient air, but supply breathing gas from another source. The three types are the self contained breathing apparatus, in which a compressed air cylinder is worn by the wearer; the supplied air respirators, where a hose supplies air from a stationary source; and combination supplied-air respirators, with an emergency backup tank.
Self-contained breathing apparatus
Supplied air respirator
Escape respirators
thumb|A simple [[Dräger (company)|Dräger escape respirator. This model has no hood, and instead comes with noseclips to ensure the wearer breathes only through the filter.]]
Smoke hood
Self-contained breathing apparatus
Continuous-flow
Self-rescue device
Issues
Under 30 CFR 11
In 1992, NIOSH published a draft report on the effectiveness of respirator regulations under the then-current 30 CFR 11. Particulate respirators back then were mainly classified as either DM, DFM, or HEPA.
Respirator risk modelling
Assigned protection factors (APF) are predicated on the assumption that users are trained in the use of their respirators, and that 100% of users exceed the APF. This "simulated workplace protection factor" (SWPF) was said to be problematic:
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:
Neither exercise was included in the OSHA fit test protocols. Put another way, it has been said:
Noncompliance with regulation
In spite of the requirement to fit test by OSHA, the following observations of noncompliance with respirator regulations were made by NIOSH and OSHA:
- Almost 80% of negative-pressure respirator wearers were not receiving fit testing.
- Over 70% of 123,000 manufacturing plants did not perform exposure-level monitoring, when selecting respirators to use in the plants.
- Noncompliance increased to almost 90% for the smallest plants.
- 75% of manufacturing plants did not have a written program.
- 56% of manufacturing plants did not have a professional respirator-program administrator (i.e., qualified individual supervising the program).
- Almost 50% of wearers in manufacturing plants did not receive an annual examination by a physician.
- Almost 50% of wearers in manufacturing plants did not receive respirator-use training.
- 80% of wearers in manufacturing plants did not have access to more than one facial-size mask, even though nearly all reusable masks were available in at least three sizes.