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A respirator is a device designed to protect the wearer from inhaling hazardous atmospheres including
fumes,
vapours,
gases
Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma).
A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...
and
particulate matter such as dusts and airborne pathogens such as
viruses
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's ...
. 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 sometimes referred to as a
filtering facepiece respirator
Mechanical filters are a class of filter for air-purifying respirators that mechanically stops particulates from reaching the wearer's nose and mouth. They come in multiple physical forms.
Mechanism of operation
Mechanical filter respirator ...
to a more robust reusable model with replaceable cartridges called an
elastomeric respirator
Elastomeric respirators, also called reusable air-purifying respirators, seal to the face with elastomeric material, which may be a natural or synthetic rubber. They are generally reusable.
Full-face versions of elastomeric respirators seal bet ...
.
Powered air-purifying respirator
A powered air-purifying respirator (PAPR) is a type of respirator used to safeguard workers against contaminated air. PAPRs consist of a headgear-and-fan assembly that takes ambient air contaminated with one or more type of pollutant or path ...
s (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
![N95-respirator-protection-types-508](https://upload.wikimedia.org/wikipedia/commons/5/5d/N95-respirator-protection-types-508.jpg)
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
Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...
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
A beard is the hair that grows on the jaw, chin, upper lip, lower lip, cheeks, and neck of humans and some non-human animals. In humans, usually pubescent or adult males are able to grow beards.
Throughout the course of history, societal at ...
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
Saccharin (''aka'' saccharine, Sodium sacchari) is an artificial sweetener with effectively no nutritional value. It is about 550 times as sweet as sucrose but has a bitter or metallic aftertaste, especially at high concentrations. Saccharin is ...
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.
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:
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
A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces. A drop may form when liquid accumulates at the lower end of a tube or other surface boundary, producing a hanging drop called a pendant d ...
, 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
The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...
(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
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Some N95 respirators have also been cleared by the
U.S. National Institute for Occupational Safety and Health
The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the ...
(NIOSH) and
U.S. Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
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
Avian influenza, known informally as avian flu or bird flu, is a variety of influenza caused by viruses adapted to birds. ,
severe acute respiratory syndrome
Severe acute respiratory syndrome (SARS) is a viral respiratory disease of zoonotic origin caused by the severe acute respiratory syndrome coronavirus (SARS-CoV or SARS-CoV-1), the first identified strain of the SARS coronavirus species, ''seve ...
(SARS),
pandemic influenza
An influenza pandemic is an epidemic of an influenza virus that spreads across a large region (either multiple continents or worldwide) and infects a large proportion of the population. There have been six major influenza epidemics in the las ...
, and
Ebola
Ebola, also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF), is a viral hemorrhagic fever in humans and other primates, caused by ebolaviruses. Symptoms typically start anywhere between two days and three weeks after becom ...
.
Escape respirators
![Escape-filter_Fluchtfilter_Dräger-Parat-3200-02](https://upload.wikimedia.org/wikipedia/commons/d/d8/Escape-filter_Fluchtfilter_Dr%C3%A4ger-Parat-3200-02.jpg)
Escape respirators or
smoke hood
A smoke hood is a hood wherein a transparent airtight bag seals around the head of the wearer while an air filter held in the mouth connects to the outside atmosphere and is used to breathe. Smoke hoods are intended to protect victims of fire fr ...
s such as Air-Purifying Escape Respirators are for use by the general public for
chemical, biological, radiological, and nuclear
Chemical, biological, radiological and nuclear defence (CBRN defence) are protective measures taken in situations in which chemical, biological, radiological or nuclear warfare (including terrorism) hazards may be present. CBRN defence consis ...
(CBRN) terrorism incidents. The
American National Standards Institute
The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organi ...
(ANSI) and the
International Safety Equipment Association
The International Safety Equipment Association (ISEA) is a trade association of manufacturers of personal protective equipment and other safety equipment, with its offices in Arlington, Virginia. More than 100 companies are members. The ISEA is t ...
(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 respirator
A powered air-purifying respirator (PAPR) is a type of respirator used to safeguard workers against contaminated air. PAPRs consist of a headgear-and-fan assembly that takes ambient air contaminated with one or more type of pollutant or pathoge ...
s (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 compound
Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...
s (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
An occupational exposure limit is an upper limit on the acceptable concentration of a hazardous substance in workplace air for a particular material or class of materials. It is typically set by competent national authorities and enforced by legi ...
but less than the
immediately dangerous to life or health
The term immediately dangerous to life or health (IDLH) is defined by the US National Institute for Occupational Safety and Health (NIOSH) as exposure to airborne contaminants that is "likely to cause death or immediate or delayed permanent advers ...
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
Firefighting is the act of extinguishing or preventing the spread of unwanted fires from threatening human lives and destroying property and the environment. A person who engages in firefighting is known as a firefighter.
Firefighters typically ...
, in
oxygen-deficient atmosphere
Inert gas asphyxiation is a form of asphyxiation which results from breathing a physiologically inert gas in the absence of oxygen, or a low amount of oxygen, rather than atmospheric air (which is composed largely of nitrogen and oxygen). Examples ...
, or in an unknown atmosphere; in these situations a
self-contained breathing apparatus
A self-contained breathing apparatus (SCBA), sometimes referred to as a compressed air breathing apparatus (CABA) or simply breathing apparatus (BA), is a device worn to provide breathable air in an atmosphere that is immediately dangerous to ...
is recommended instead.
Types of filtration
Mechanical filter
Mechanical filter respirators retain particulate matter such as dust created during
woodwork
Woodworking is the skill of making items from wood, and includes cabinet making (cabinetry and furniture), wood carving, joinery, carpentry, and woodturning.
History
Along with stone, clay and animal parts, wood was one of the first materials ...
ing 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
Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respectiv ...
that attracts and holds particles on the filter surface.
There are many different filtration standards that vary by jurisdiction. In the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, the
National Institute for Occupational Safety and Health
The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
defines the categories of particulate filters according to their
NIOSH air filtration rating
The NIOSH air filtration rating is the U.S. National Institute for Occupational Safety and Health (NIOSH)'s classification of filtering respirators. The ratings describe the ability of the device to protect the wearer from solid and liquid pa ...
. The most common of these are the
N95 respirator
An N95 filtering facepiece respirator, commonly abbreviated N95 respirator, is a particulate-filtering facepiece respirator that meets the U.S. National Institute for Occupational Safety and Health (NIOSH) N95 classification of air filtratio ...
, which filters at least 95% of
airborne particles
Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The te ...
but is not resistant to
oil
An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...
.
Other categories filter 99% or 99.97% of particles, or have varying degrees of resistance to oil.
In the
European Union
The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...
,
European standard
European Standards (abbreviated EN, from the German name ("European Norm")) are technical standards which have been ratified by one of the three European standards organizations: European Committee for Standardization (CEN), European Committee for ...
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
The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
-approved respirators never include earloops because they don't provide enough support to establish a reliable, airtight seal.) Those standards include the Chinese KN95, Australian / New Zealand P2, Korean 1st Class also referred to as KF94, and Japanese DS.
Chemical cartridge
![Respirator canister with ESLI for asid gases -1](https://upload.wikimedia.org/wikipedia/commons/8/80/Respirator_canister_with_ESLI_for_asid_gases_-1.JPG)
Chemical cartridge respirators use a cartridge to remove gases,
volatile organic compound
Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...
s (VOCs), and other vapors from breathing air by
adsorption
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a f ...
,
absorption
Absorption may refer to:
Chemistry and biology
* Absorption (biology), digestion
**Absorption (small intestine)
*Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials
*Absorption (skin), a route by which ...
, or
chemisorption
Chemisorption is a kind of adsorption which involves a chemical reaction between the surface and the adsorbate. New chemical bonds are generated at the adsorbent surface. Examples include macroscopic phenomena that can be very obvious, like cor ...
. A typical
organic
Organic may refer to:
* Organic, of or relating to an organism, a living entity
* Organic, of or relating to an anatomical organ
Chemistry
* Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...
vapor respirator cartridge is a metal or plastic case containing from 25 to 40 grams of sorption media such as
activated charcoal
"Activated" is a song by English singer Cher Lloyd. It was released on 22 July 2016 through Vixen Records. The song was made available to stream exclusively on ''Rolling Stone'' a day before to release (on 21 July 2016).
Background
In an interv ...
or certain
resin
In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on natu ...
s. 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.
[ The document describes the methods used previously and currently used to perform the timely replacement of cartridges in air purifying respirators.]
If the concentration of harmful gases is
immediately dangerous to life or health
The term immediately dangerous to life or health (IDLH) is defined by the US National Institute for Occupational Safety and Health (NIOSH) as exposure to airborne contaminants that is "likely to cause death or immediate or delayed permanent advers ...
, in workplaces covered by the
Occupational Safety and Health Act
The Occupational Safety and Health Act of 1970 is a US labor law governing the federal law of occupational health and safety in the private sector and federal government in the United States. It was enacted by Congress in 1970 and was signed by P ...
the US
Occupational Safety and Health Administration
The Occupational Safety and Health Administration'' (OSHA ) is a large regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...
specifies the use of air-supplied respirators except when intended solely for escape during emergencies.
[OSHA standar]
29 CFR 1910.134
"Respiratory Protection" NIOSH
The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
also discourages their use under such conditions.
Form factors
Filtering facepiece
![Atemluftfilter Einwegmaske](https://upload.wikimedia.org/wikipedia/commons/4/48/Atemluftfilter_Einwegmaske.jpg)
Filtering facepiece respirators are discarded when they become unsuitable for further use due to considerations of hygiene, excessive resistance, or physical damage.
These are typically simple, light, single-piece, half-face masks and employ the first three mechanical filter mechanisms in the list above to remove particulates from the air stream. The most common of these is the white, disposable Standard N95 variety; another type is the blue,
Surgical N95 mask. It is discarded after single use or some extended period depending on the contaminant.
Elastomeric
![Police officer wearing half-mask respirator](https://upload.wikimedia.org/wikipedia/commons/0/0d/Police_officer_wearing_half-mask_respirator.jpg)
Elastomeric respirators are reusable because the facepiece is cleaned and reused, but the filter cartridges are discarded and replaced when they become unsuitable for further use.
These are replaceable-cartridge, multiple-use models. Typically one or two cartridges attach securely to a mask which has built into it a corresponding number of valves for inhalation and one for exhalation.
Powered air-purifying respirators
Powered air-purifying respirator
A powered air-purifying respirator (PAPR) is a type of respirator used to safeguard workers against contaminated air. PAPRs consist of a headgear-and-fan assembly that takes ambient air contaminated with one or more type of pollutant or path ...
s (PAPRs) have a battery-powered blower that moves the airflow through the filters.
They take
contaminate
Contamination is the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical body, natural environment, workplace, etc.
Types of contamination
Wi ...
d air, remove a certain quantity of pollutants and return the air to the user. There are different units for different environments. The units consist of a powered
fan which forces incoming air through one or more
filter
Filter, filtering or filters may refer to:
Science and technology
Computing
* Filter (higher-order function), in functional programming
* Filter (software), a computer program to process a data stream
* Filter (video), a software component tha ...
s to the user for breathing. The fan and filters may be carried by the user or they may be remotely mounted and the user breathes the air through tubing.
The filter type must be matched to the contaminants that need to be removed. Some PAPR's are designed to remove fine particulate matter, while others are suitable for working with
volatile organic compound
Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...
s as those in
spray paint
Aerosol paint (commonly spray paint) is paint that comes in a sealed, pressurized container and is released in an aerosol spray when a valve button is depressed. Aerosol painting is one form of spray painting; it leaves a smooth, even coat, unlike ...
s. These must have their filter elements replaced more often than a particulate filter.
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 respirators that integrate both types.
According to the NIOSH Respirator Selection Logic, atmosphere-supplying are recommended for concentrations of hazardous particulates or gases that are greater than the
immediately dangerous to life or health
The term immediately dangerous to life or health (IDLH) is defined by the US National Institute for Occupational Safety and Health (NIOSH) as exposure to airborne contaminants that is "likely to cause death or immediate or delayed permanent advers ...
level; where the required
assigned protection factor exceeds those of air-purifying respirators; during
firefighting
Firefighting is the act of extinguishing or preventing the spread of unwanted fires from threatening human lives and destroying property and the environment. A person who engages in firefighting is known as a firefighter.
Firefighters typically ...
(self-contained breathing apparatuses only); in
oxygen-deficient atmosphere
Inert gas asphyxiation is a form of asphyxiation which results from breathing a physiologically inert gas in the absence of oxygen, or a low amount of oxygen, rather than atmospheric air (which is composed largely of nitrogen and oxygen). Examples ...
; and in an unknown atmosphere.
Self-contained breathing apparatus
A self-contained breathing apparatus (SCBA) typically has three main components: a high-pressure air cylinder (e.g., 2200 psi to 4500 psi), a pressure gauge and regulator, and an inhalation connection (mouthpiece, mouth mask or full face mask), connected together and mounted to a carrying frame or a harness with adjustable shoulder straps and belt so it can be worn on the back. There are two kinds of SCBA: open circuit and closed circuit. Most modern SCBAs are open-circuit.
Open-circuit industrial breathing sets are filled with filtered, compressed air. The compressed air passes through a regulator, is inhaled and exhaled out of the circuit, quickly depleting the supply of air. Air cylinders are made of aluminum, steel, or of a composite construction like fiberglass-wrapped aluminum. The "positive pressure" type is common, which supplies a steady stream of air to stop fumes or smoke from leaking into the mask. Other SCBA's are of the "demand" type, which only supply air when the regulator senses the user inhaling. All fire departments and those working in toxic environments use the positive pressure SCBA for safety reasons.
The closed-circuit type SCBA filters, supplements, and recirculates exhaled gas like a
rebreather
A rebreather is a breathing apparatus that absorbs the carbon dioxide of a user's breathing, exhaled breath to permit the rebreathing (recycling) of the substantially unused oxygen content, and unused inert content when present, of each breath. ...
. It is used when a longer-duration supply of breathing gas is needed, such as in mine rescue and in long tunnels, and going through passages too narrow for a large open-circuit air cylinder.
Supplied air respirator
Supplied air respirators make use of a hose to deliver air from a stationary source. It provides clean air for long periods of time and are light weight for the user, although it limits user mobility. They are normally used when there are extended work periods required in atmospheres that are not immediately dangerous to life and health (IDLH).
Disadvantages
Extended use of respirators can result in higher levels of
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
than recommended in a work environment,
[copy]
/ref> and can lead to headache
Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches.
Headaches can occur as a result ...
s, dermatitis
Dermatitis is inflammation of the skin, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened. The area of skin involved can v ...
and acne
Acne, also known as ''acne vulgaris'', is a long-term Cutaneous condition, skin condition that occurs when Keratinocyte, dead skin cells and Sebum, oil from the skin clog hair follicles. Typical features of the condition include comedo, black ...
.
Regulation
The choice and use of respirators in developed countries is regulated by national legislation. To ensure that employers choose respirators correctly, and perform high-quality respiratory protection programs, various guides and textbooks have been developed:
For standard filter classes used in respirators, see Mechanical filter (respirator)#Filtration standards.
History
Earliest records to 19th century
The history of protective respiratory equipment can be traced back as far as the first century, when Pliny the Elder
Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic '' ...
(–79) described using animal bladder skins to protect workers in Roman mines from red lead oxide dust. In the 16th century, Leonardo da Vinci
Leonardo di ser Piero da Vinci (15 April 14522 May 1519) was an Italian polymath of the High Renaissance who was active as a painter, Drawing, draughtsman, engineer, scientist, theorist, sculptor, and architect. While his fame initially res ...
suggested that a finely woven cloth dipped in water could protect sailors from a toxic weapon made of powder that he had designed.
In 1785, Jean-François Pilâtre de Rozier
Jean-François Pilâtre de Rozier () was a French chemistry and physics teacher, and one of the first pioneers of aviation. He made the first manned free balloon flight with François Laurent d'Arlandes on 21 November 1783, in a Montgolfier bal ...
invented a respirator.
Alexander von Humboldt
Friedrich Wilhelm Heinrich Alexander von Humboldt (14 September 17696 May 1859) was a German polymath, geographer, naturalist, explorer, and proponent of Romantic philosophy and science. He was the younger brother of the Prussian minister, p ...
introduced a primitive respirator in 1799 when he worked as a mining engineer in Prussia.
Practically all respirators in the early 18th century consisted of a bag placed completely over the head, fastened around the throat with windows through which the wearer could see. Some were rubber
Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
, some were made of rubberized fabric, and still others of impregnated fabric, but in most cases a tank of compressed air or a reservoir of air under slight pressure was carried by the wearer to supply the necessary breathing air. In some devices certain means were provided for the adsorption of carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
in exhaled air and the rebreathing of the same air many times; in other cases valves allowed exhalation of used air.
Julius Jeffreys first used the word "respirator" as a mask in 1836. The mask worked by capturing moisture and warmth in exhaled air in a grid of fine metal wires. Inhaled air then was warmed and moistened as it passed through the same metal grid, providing relief to people with lung diseases. The Respirator became popular, and was mentioned in the literature of the day, including in the writings of Elizabeth Gaskell
Elizabeth Cleghorn Gaskell (''née'' Stevenson; 29 September 1810 – 12 November 1865), often referred to as Mrs Gaskell, was an English novelist, biographer and short story writer. Her novels offer a detailed portrait of the lives of many st ...
, William Makepeace Thackeray
William Makepeace Thackeray (; 18 July 1811 – 24 December 1863) was a British novelist, author and illustrator. He is known for his satirical works, particularly his 1848 novel '' Vanity Fair'', a panoramic portrait of British society, and t ...
and Charles Dickens
Charles John Huffam Dickens (; 7 February 1812 – 9 June 1870) was an English writer and social critic. He created some of the world's best-known fictional characters and is regarded by many as the greatest novelist of the Victorian e ...
.
In 1848, the first US patent for an air-purifying respirator was granted to Lewis P. Haslett
Lewis Phectic Haslett was an American inventor and the first person to receive a patent
A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a lim ...
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
Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...
substance. Following Haslett, a long string of patents were issued for air purifying devices, including patents for the use of cotton fibers as a filtering medium, for charcoal and lime absorption of poisonous vapors, and for improvements on the eyepiece and eyepiece assembly. Hutson Hurd patented a cup-shaped mask in 1879 which became widespread in industrial use, and Hurd's H.S. Cover Company was still in business in the 1970s.
Inventors in Europe included John Stenhouse
John Stenhouse FRS FRSE FIC FCS (21 October 1809 – 31 December 1880) was a Scottish chemist. In 1854, he invented one of the first practical respirators.
He was a co-founder of the Chemical Society in 1841.
Life
John Stenhouse was born ...
, 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
"Activated" is a song by English singer Cher Lloyd. It was released on 22 July 2016 through Vixen Records. The song was made available to stream exclusively on ''Rolling Stone'' a day before to release (on 21 July 2016).
Background
In an interv ...
to become the most widely used filter for respirators. Irish physicist John Tyndall
John Tyndall FRS (; 2 August 1820 – 4 December 1893) was a prominent 19th-century Irish physicist. His scientific fame arose in the 1850s from his study of diamagnetism. Later he made discoveries in the realms of infrared radiation and the p ...
took Stenhouse's mask, added a filter of cotton wool saturated with lime
Lime commonly refers to:
* Lime (fruit), a green citrus fruit
* Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide
* Lime (color), a color between yellow and green
Lime may also refer to:
Botany ...
, glycerin
Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
, 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
The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
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.' German Bernhard Loeb patented several inventions to 'purify foul or vitiated air,' and counted the Brooklyn Fire Department
The Brooklyn Fire Department (BFD) was a professional fire department that provided fire protection and rescue services to the city of Brooklyn, New York, within modern-day New York City, from 1869 to 1898. The Brooklyn Fire Department, a paid ...
among his customers.
A predecessor of the N95 was a design by Doctor Lien-teh Wu who was working for the Chinese Imperial Court in the fall of 1910, which was the first that protected users from bacteria in empirical testing. Subsequent respirators were reusable but bulky and uncomfortable. In the 1970s, the Bureau of Mines and NIOSH developed standards for single-use respirators, and the first N95 respirator was developed by 3M and approved in 1972.
World War I
The first recorded response and defense against chemical attacks using respirators occurred during the Second Battle of Ypres
During the First World War, the Second Battle of Ypres was fought from for control of the tactically important high ground to the east and south of the Flemish town of Ypres in western Belgium. The First Battle of Ypres had been fought the pre ...
on the Western Front in World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
. It was the first time Germany used chemical weapon
A chemical weapon (CW) is a specialized munition that uses chemicals formulated to inflict death or harm on humans. According to the Organisation for the Prohibition of Chemical Weapons (OPCW), this can be any chemical compound intended as a ...
s on a large scale releasing 168 tons of chlorine gas
Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is ...
over a four-mile (6 km) front killing around 6,000 troops within ten minutes through asphyxiation
Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects primarily the tissues and organs. There are many circumstances that can i ...
. The gas being denser than air flowed downwards forcing troops to climb out of their trenches
A trench is a type of excavation or in the ground that is generally deeper than it is wide (as opposed to a wider gully, or ditch), and narrow compared with its length (as opposed to a simple hole or pit).
In geology, trenches result from erosi ...
. Reserve Canadian troops, who were away from the attack, used urine
Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excretion, excreted from the body through the urethra.
Cel ...
-soaked cloths as primitive respirators. A Canadian soldier realized that the ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
in urine would react with the chlorine, neutralizing it, and that the water would dissolve the chlorine, allowing soldiers to breathe through the gas.
21st century
China normally makes 10 million masks per day, about half of the world production. During the COVID-19 pandemic
The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identif ...
, 2,500 factories were converted to produce 116 million daily.
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.
See also
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References
Bibliography
* ''Nancy Bollinger, Robert Schutz et al.'
NIOSH Guide to Industrial Respiratory Protection.
— NIOSH. — Cincinnati, Ohio: DHHS (NIOSH) Publication No. 87-116, 1987. — 305 p.
* ''Linda Rosenstock et al.'
TB Respiratory Protection Program In Health Care Facilities. Administrator's Guide.
— DHHS (NIOSH) Publication No. 99-143. — Cincinnati, Ohio, 1999. — 120 p.
* ''Nancy Bollinger et al.'
NIOSH Respirator Selection Logic.
— DHHS (NIOSH) Publication No. 2005-100. — Cincinnati, Ohio, 2004. — 39 p
Respiratory protective equipment at work. A practical guide. 4 ed.
— HSE (UK). — Norwich: Crown, 2013. — 59 p. — .
BGR/GUV-R 190 Benutzung von Atemschutzgeräten.
— Deutsche Gesetzliche Unfallversicherung e.V. (DGUV), Medienproduktion. — Berlin (BRD), 2011. — 174 p.
* ''Jaime Lara, Mireille Vennes''
Guide pratique de protection respiratoire.
— Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST). — Montréal (Canada), 2002. — 56 p. —
Further reading
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NIOSH respirators main page
What's Special about Chemical, Biological, Radiological, and Nuclear (CBRN) Air-Purifying Respirators (APR)?
NIOSH
The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
Fact Sheet
NIOSH-Approved Disposable Particulate Respirators (Filtering Facepieces)
TSI Application note ITI-041: Mechanisms of Filtration for High Efficiency Fibrous Filters
* British Standard
British Standards (BS) are the standards produced by the BSI Group which is incorporated under a royal charter and which is formally designated as the national standards body (NSB) for the UK. The BSI Group produces British Standards under the a ...
BS EN 143:2000: Respiratory protective devices – Particle filters – Requirements, testing, marking
* British Standard
British Standards (BS) are the standards produced by the BSI Group which is incorporated under a royal charter and which is formally designated as the national standards body (NSB) for the UK. The BSI Group produces British Standards under the a ...
BS EN 149:2001: Respiratory protective devices – Filtering half masks to protect against particles – Requirements, testing, marking
External links
3M Safety Respirator Classification Guide
3M.com
Mine Safety Appliance Company (MSA) Respirator Classification Guide
MSA.com
cdc.gov/niosh
ccohs.ca
*The following links are respirator selection logic and competitive bid research information pages for Chemical, Biological, Radiological, and Nuclear (CBRN) defense responders:
Air-Purifying Respirators (APR)
cdc.gov/niosh. Respirator manufacturer approvals for NIOSH-certified air-purifying respirator with CBRN Protections (CBRN APR). This link covers APR and Air-Purifying Escape Respirators (APER) certified by the NIOSH's National Personal Protective Technology Laboratory (NPPTL), Pittsburgh, PA, to CBRN protection NIOSH standards. CBRN APR are tight-fitting, full-face respirators with approved accessories and protect the user breathing zone by relying on user negative pressure, fit testing and user seal checks to filter less than Immediately Dangerous to Life and Health (IDLH) concentrations of hazardous respiratory compounds and particulates through NIOSH CBRN Cap 1, Cap 2 or Cap 3 canisters for CBRN APR- or CBRN 15- or CBRN 30-rated APER.
PAPR
cdc.gov/niosh. Respirator manufacturer approvals for NIOSH-certified powered air-purifying respirator with CBRN Protections (CBRN PAPR-loose fitting or tight fitting)
osha.gov
* Occupational Safety & Health Administration, Respiratory Protectio
brinkster.com
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