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 microorganisms. There are two main categories: 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 sometimes referred to as a dust mask to more robust reusable models with replaceable cartridges often called a gas mask.
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 design impact the respirator assigned protection factors, i.e. the resulting degree of protection from which kind of hazard.
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.
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.
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. A high-quality respirator should see TIL of only around 5%. 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
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 and KF94
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," providing respiratory protection to the wearer as well.
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.
The difference between N95 and KF94 standards is that KF94 is used in South Korean (that provides a super high quality of face respirators). Both of these standards are filtering up to 99%.
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