respirator respirator a respirator is a device designed to protect the wearer from inhaling hazardous atmospheres including fumes, vapours, 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. for the mechanical device used to assist breathing, see ventilator. for the mask worn during surgery, see surgical mask. white, disposable standard n95 filtering facepiece respirator a half-face elastomeric air-purifying respirator. this kind of respirator is reusable, with the filters being replaced periodically. lab worker wearing a powered air-purifying respirator air-purifying respirators range from relatively inexpensive, single-use, disposable face masks sometimes referred to as a filtering facepiece respirator to a more robust reusable model with replaceable cartridges called an elastomeric respirator. powered air-purifying respirators (papr), use a pump or fan to constantly move air through a filter and supply purified air into a mask, helmet or hood. physical form types of respirators by physical form. click to enlarge. 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. the differences in respirator designs impact the respirator assigned protection factors, i.e. the resulting degree of protection from specific kinds of hazards. 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. for example, someone who is spray painting could wear a half-face respirator, but someone who works with chlorine gas would have to wear a full-face respirator. use 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, shipbuilding, and the textile industry. respirators require user training in order to provide proper protection. user seal check 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 by specially trained personnel 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 most types of respirators depend upon forming a good seal between the respirator body and the face of the wearer. fit testing procedures have been developed to ensure that the respirator is appropriate for the wearer and the wearer's donning technique is capable of creating an adequate seal. poor fit can have a negative impact on the respirator's overall filtering effectiveness by as much as 65%. a study on respirator effectiveness conducted in beijing found that facial fit was the primary contributor to total inward leakage (til), based on a test of nine different models. facial hair such as a beard can interfere with proper fit. qualitative fit testing typically subjects the wearer to an atmosphere containing an aerosol that can be detected by the wearer, such as saccharin or isoamyl acetate, with the wearer reporting whether detectable levels of the aerosol has penetrated into the breathing area. quantitative fit testing typically uses a specially prepared respirator with an inserted probe. the respirator is donned, and aerosol concentrations inside and outside of the mask are compared and used to determine a numerical fit factor. typical room atmosphere contains sufficient particulates to perform the test, but aerosol generators can be used to improve the test accuracy.workplace protection factor (pf) of filtering facepiece, measured in real time with two optical dust meters. in-facepiece dust concentration is changed dozens of times in a matter of minutes due to changes of the size of the gaps between the mask and face. 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: it is well known how ineffective ... trying to compensate the harmful workplace conditions with ... the use of respirators by employees. unfortunately, the only certain way of reducing the exceedance fraction to zero is to ensure that co (note: co - concentration of pollutants in the breathing zone) never exceeds the pel value. the very limited field tests of air-purifying respirator performance in the workplace show that respirators may perform far less well under actual use conditions than is indicated by laboratory fit factors. we are not yet able to predict the level of protection accurately; it will vary from person to person, and it may also vary from one use to the next for the same individual. in contrast, we can predict the effectiveness of engineering controls, and we can monitor their performance with commercially available state-of-the-art devices. contrast with surgical mask an infographic on the difference between surgical masks and n95 respirators a surgical mask is a loose-fitting, disposable device that creates a physical barrier between the mouth and nose of the wearer and potential contaminants in the immediate environment. if worn properly, a surgical mask is meant to help block large-particle droplets, splashes, sprays, or splatter that may contain viruses and bacteria. surgical masks may also help reduce exposure from the wearer's saliva and respiratory secretions to others, especially during surgical procedures. a surgical mask, by design, does not filter or block very small particles from the outside air that may be transmitted by coughs, sneezes, or certain medical procedures to the wearer. surgical masks also do not provide complete protection from germs and other contaminants because of the loose fit between the surface of the face mask and the face. collection efficiency of surgical mask filters can range from less than 10% to nearly 90% for different manufacturers' masks when measured using the test parameters for niosh certification. however, a study found that even for surgical masks with "good" filters, 80–100% of subjects failed an osha-accepted qualitative fit test, and a quantitative test showed 12–25% leakage. the u.s. centers for disease control and prevention (cdc) recommends surgical masks in procedures where there can be an aerosol generation from the wearer, if small aerosols can produce a disease to the patient. surgical n95 astronaut kate rubins wearing a 3m 1860 "surgical n95" respirator some n95 respirators have also been cleared by the u.s. national institute for occupational safety and health (niosh) and u.s. food and drug administration as surgical and are labeled "surgical n95", "medical respirators," or "healthcare respirators". these protect the patient and others from the wearer's respiratory emissions (as a surgical mask would) as well as protect the wearer from airborne particulates and aerosols (as a standard n95 respirator). unlike a standard n95 respirator, fda-cleared "healthcare respirators" also provide protection from high-pressure streams or jets of bodily fluid, such as blood. the cdc recommends the use of respirators with at least n95 certification to protect the wearer from inhalation of infectious particles including mycobacterium tuberculosis, avian influenza, severe acute respiratory syndrome (sars), pandemic influenza, and ebola. escape respirators a simple dräger escape respirator. this model has no hood, and instead comes with noseclips to ensure the wearer breathes only through the filter. escape respirators or smoke hoods such as air-purifying escape respirators are for use by the general public for chemical, biological, radiological, and nuclear (cbrn) terrorism incidents. the american national standards institute (ansi) and the international safety equipment association (isea) established the american national standard for air-purifying respiratory protective smoke escape devices to define both test criteria and approval methods for fire/smoke escape hoods. ansi/isea standard 110 provides design guidance to manufacturers of respiratory protective smoke escape devices (rped) in the form of performance requirements and testing procedures. the standard covers certification, iso registration for the manufacturer, associated test methods, labeling, conditioning requirements, independent process and quality control audits, and follow-up inspection programs. ansi/isea 110 was prepared by members of the isea rped group, in consultation with testing laboratories and was reviewed by a consensus panel representing users, health and safety professionals and government representatives. the u.s. consumer product safety commission uses ansi/isea 110 as the benchmark in their testing of fire escape masks. air-purifying respirators 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 are used against particulates, gases, and vapors that are at atmospheric concentrations less than immediately dangerous to life and health. they may be negative-pressure respirators driven by the wearer's inhalation and exhalation, or positive-pressure units such as powered air-purifying respirators (paprs). air-purifying respirators may use one or both of two kinds of filtration: mechanical filters retain particulate matter, while chemical cartridges remove gases, volatile organic compounds (vocs), and other vapors. additionally, air-purifying respirators may come in many forms: filtering facepiece respirators consist solely of a disposable mechanical filter; elastomeric respirators are reusable but have replaceable filters attached to the mask; and powered air-purifying respirators have a battery-powered blower that moves the airflow through the filters. 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 filter main article: mechanical filter respiratormechanical filter respirators retain particulate matter such as dust created during woodworking or metal processing, when contaminated air is passed through the filter material. since the filters cannot be cleaned and reused and have a limited lifespan, cost and disposability are key factors. single-use, disposable and replaceable cartridge models exist. 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