Editing Respirator (section)

=== 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>