Editing Respirator (section)

== Types of filtration ==

=== Mechanical filter ===
: ''Main Article: [[Mechanical filter respirator|Mechanical filter respirator (and regulatory ratings)]]'' <!-- So don't put 'N95' here! -->

[[File:What it Means to be NIOSH-Approved - A look into N95 Certification Testing.webm|thumb|right|300px|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&nbsp;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.<ref name="fact sheet">{{cite journal | last1 = Metzler | first1 = R | last2 = Szalajda | first2 = J | title = NIOSH Fact Sheet: NIOSH Approval Labels - Key Information to Protect Yourself | journal = DHHS (NIOSH) Publication No. 2011-179 | year = 2011 | url = https://www.cdc.gov/niosh/docs/2011-179/pdfs/2011-179.pdf | issn = 0343-6993 | access-date = 10 September 2017 | archive-date = 20 July 2018 | archive-url = https://web.archive.org/web/20180720182756/https://www.cdc.gov/niosh/docs/2011-179/pdfs/2011-179.pdf | url-status = live }}</ref>

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 mask]]s.<ref>{{cite web |title=A Guide to Respiratory Protective Equipment |url=https://www.hsa.ie/eng/Publications_and_Forms/Publications/Chemical_and_Hazardous_Substances/Respiratory%20Protective%20Equipment.pdf |website=hsa.ie |access-date=12 July 2024 |archive-date=30 June 2024 |archive-url=https://web.archive.org/web/20240630012837/https://www.hsa.ie/eng/Publications_and_Forms/Publications/Chemical_and_Hazardous_Substances/Respiratory%20Protective%20Equipment.pdf |url-status=live }}</ref>

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.<ref>{{Cite web|url=https://multimedia.3m.com/mws/media/1791500O/comparison-ffp2-kn95-n95-filtering-facepiece-respirator-classes-tb.pdf|title=Technical Bulletin: Comparison of FFP2, KN95, and N95 and Other Filtering Facepiece Respirator Classes|date=January 2020|publisher=3M Personal Safety Division|access-date=3 April 2020|archive-date=14 April 2020|archive-url=https://web.archive.org/web/20200414004708/https://multimedia.3m.com/mws/media/1791500O/comparison-ffp2-kn95-n95-filtering-facepiece-respirator-classes-tb.pdf|url-status=live}}</ref>

=== Canister or chemical cartridge ===
[[File:Respirator canister with ESLI for asid gases -1.JPG|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 [[Cartridges and canisters of air-purifying respirators#End-of-service-life indicators (ESLI)|end-of-service-life indicator, ESLI]]).|alt=]]
{{Main|Chemical cartridge|NIOSH air filtration rating#Chemical cartridge and canister classifications|Gas mask}}

[[Chemical cartridge]]s and [[gas mask]] canisters remove gases, [[volatile organic compound]]s (VOCs), and other vapors from breathing air by [[adsorption]], [[absorption (chemistry)|absorption]], or [[chemisorption]].  A typical [[organic compound|organic]] vapor respirator cartridge is a metal or plastic case containing from 25 to 40&nbsp;grams of sorption media such as [[activated charcoal]] or certain [[resin]]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.<ref name="CartridgesReplacement">[[:File:Methods for the timely replacement of cartridges in respirators.pdf|The document describes the methods used previously and currently used to perform the timely replacement of cartridges in air purifying respirators.]]</ref>{{Primary source inline|reason=Unambiguous original research|date=January 2025}}

If the concentration of harmful gases is [[IDLH|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.<ref name="Standard">OSHA standard [http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=12716 29 CFR 1910.134] {{Webarchive|url=https://web.archive.org/web/20140924184743/https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=12716 |date=24 September 2014 }} "Respiratory Protection"</ref> [[NIOSH]] also discourages their use under such conditions.<ref name="Учебник-по-выбору-2004">{{cite book|last=Bollinger|first=Nancy|title=NIOSH Respirator Selection Logic|url=https://www.cdc.gov/niosh/docs/2005-100/|series=DHHS (NIOSH) Publication No. 2005-100|year=2004|publisher=National Institute for Occupational Safety and Health|location=Cincinnati, Ohio|pages=32|display-authors=etal|doi=10.26616/NIOSHPUB2005100|access-date=10 September 2017|archive-date=23 June 2017|archive-url=https://web.archive.org/web/20170623115207/https://www.cdc.gov/niosh/docs/2005-100/|url-status=live}}</ref>
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