science

NIOSH air filtration rating

NIOSH air filtration rating is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand NIOSH air filtration rating rather than just read about it. In short: The NIOSH air filtration rating is the U.S. National Institute for Occupational Safety and Health (NIOSH)'s classification of filtering respirators.

Key takeaways

NIOSH air filtration rating belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect NIOSH air filtration rating to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NIOSH air filtration rating from memory before moving on to harder problems.

Reference excerpt

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 particulates in the air. The certification and approval process for respiratory protective devices is governed by Part 84 of Title 42 of the Code of Federal Regulations (42 CFR 84). Respiratory protective devices so classified include air-purifying respirators (APR) such as filtering facepiece respirators and chemical protective cartridges that have incorporated particulate filter elements. The NIOSH-provided classifications only cover the filtration of particles or aerosols, not the air-purifying respirator's ability to remove chemical gasses and vapors from air, which is regulated under 42 CFR 84 Subpart L. For chemical cartridge classifications, NIOSH, under 42 CFR 84, partially defers to American National Standard ANSI K13.1-1973. All classifications assume that the respirator is properly fitted.

NIOSH ratings trademark

It is illegal in the United States to use filtration terms coined under 42 CFR 84, or mark masks with the word "NIOSH" without the approval of NIOSH. Information about approved respirators can be found in the NIOSH certified equipment list (CEL).

Early NIOSH/USBM classifications

30 CFR 14 Schedule 21

30 CFR 11

Prior to the approval of 42 CFR 84, MSHA and NIOSH approved respirators under 30 CFR 11. Non-powered respirator filters were classified based on their design against a contaminant, including substances like Dusts, Fumes, Mists, radionuclides, and asbestos. Dust/Mist was usually tested with silica, and Fume was usually tested with lead fume. The most popular respirator filters were often referred to as DM (Dust/Mist) or DFM (Dust/Fume/Mist) in CDC and NIOSH literature as shorthand. Non-powered filters were also classified under the HEPA specification, if applicable. Only 30 CFR 11 HEPA filters were permitted by NIOSH for the prevention of tuberculosis[C3] and asbestos-related diseases.[CF1] NIOSH was concerned about users choosing inappropriate respirators, like confusion over choosing DM or DFM respirators with regards to particle penetration, so proposed Part 84 rules in 1994 dropped the contaminant/HEPA classification for most respirators in favor of three specifications, Type A, B and C, each representing filtration of 99.97%, 99%, and 95% respectively, with Type A proposed to be used in place of HEPA for non-powered respirators.[C1] In 1973, the Los Alamos National Laboratory (LANL) recommended NIOSH use NaCl aerosol to test DM and DFM filters. Results from those tests showed significant leakage, with efficiency levels measured at around 75% to 90%. LANL noted that lead fume would plug the tested filters, increasing the apparent filtration efficiency of the filter.

Transition

Current classifications

42 CFR 84

Under the current revision of Part 84 established in 1995, NIOSH established nine classifications of approved particulate filtering respirators based on a combination of the respirator series and efficiency level. The first part of the filter's classification indicates the series using the letters N, R, or P to indicate the filter's resistance to filtration efficiency degradation when exposed to oil-based or oil-like aerosols (e.g., lubricants, cutting fluids, glycerine, etc.).[CF2][N2] Definitions and intended use for each series is indicated below.

N for not resistant to oil. Used when oil particulates are not present. Tested using sodium chloride particles. R for resistant to oil. Used when oil particulates are present and the filter is disposed of after one shift. Tested using dioctyl phthalate (DOP) oil particles. P for oil-proof. Used when oil particulates are present and the filter is re-used for more than one shift. Tested with DOP oil particles. The second value indicates the minimum efficiency level of the filter. When tested according to the protocol established by NIOSH each filter classification must demonstrate the minimum efficiency level indicated below.

All respirator types are permitted for TB.[C1] Class-100 filters can block asbestos.[CF1][S2] For N type filters, a 200 mg load of NaCl is used, with an undefined service time. For R type filters, a 200 mg of DOP is used, with a defined service time of "one work shift". For P type filters, an indefinite amount of DOP is used until filtration efficiency stabilizes.[N2] P100 filters, under 42 CFR part 84, are the only filters permitted to be magenta in color. HE (high-efficiency) labeled filters (described in the subsection) are only provided for powered air-purifying respirators. HE-marked filters are 99.97% efficient against 0.3 micron particles and are oil-proof. Since filters are tested against the by definition most penetrating particle size of 0.3 μm, an APR with a P100 classification would be at least 99.97% efficient at removing particles of this size.[N2] Particles with a size both less than and greater than 0.3 μm may be filtered at an efficiency greater than 99.97%.[N2] However, this may not always be the case, as the most penetrating particle size for N95s was measured to be below 0.1 μm, as opposed to the predicted size of between 0.1 and 0.3 μm.

2020 powered air-purifying respirator update

Chemical cartridge and canister classifications

… excerpt ends here. Continue reading the full article.

Illustrations

Example Part 84 Label, TC-84A particulate, with older NIOSH logo, for P100 respirator, equivalent to Part 11 HEPA.

Worked examples

Example 1 — a first encounter with NIOSH air filtration rating

Start with the simplest possible case. Write down what NIOSH air filtration rating claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to NIOSH air filtration rating before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about NIOSH air filtration rating ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of NIOSH air filtration rating

In research: NIOSH air filtration rating appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses NIOSH air filtration rating in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: NIOSH air filtration rating is common in secondary-school and first-year university syllabi. It links to neighbouring topics Air pollution, National Institute for Occupational Safety and Health, Occupational safety and health, so understanding it makes those chapters shorter.
In everyday life: Look for NIOSH air filtration rating outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “NIOSH air filtration rating” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study NIOSH air filtration rating in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NIOSH air filtration rating means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain NIOSH air filtration rating out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NIOSH air filtration rating in simple terms?

The NIOSH air filtration rating is the U.S. National Institute for Occupational Safety and Health (NIOSH)'s classification of filtering respirators.

Why does NIOSH air filtration rating matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study NIOSH air filtration rating?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on NIOSH air filtration rating.