The term “N95” is used often when it comes to disposable respirators, however many people don’t fully understand its meaning. The “N95” is a rating that’s derived from the National Institute for Occupational Safety and Health (NIOSH) classification system for particulate filters, which includes disposable respirators as well as filters for reusable respirators. This rating system uses three letters and three numbers: N, R, and P, along with 95, 99, and 100. Combining a letter with a number gives you a rating that tells you the filtering media’s resistance to oil and its filtration efficiency. Here is a key to help decode those letters and numbers:

Letters – Resistance to oil mist

• N - Not resistant to oily mist

• R - Resistant to oily mist

• P - oil Proof

Numbers – efficiency against certain particles

• 95 – filter provides at least 95% filtration efficiency

• 99 - provides at least 99% filtration efficiency

• 100 - provides at least 99.97% filtration efficiency

For example, a disposable respirator that’s labeled “N95” is NIOSH-approved to be at least 95% efficient at filtering out certain solid dusts and liquid mists that do not contain oil. A P100 is NIOSH-approved to help filter at least 99.97% of certain solid particles and liquid mists, as well as those containing oil.


NIOSH also has a classification system for cartridges that are used on reusable respirators. However, it utilizes color codes rather than letters and numbers to designate what specific contaminants the cartridges can help filter out. Below are just a few of the common respirator cartridge label colors and their meaning.

These colors are standard in the industry and can be found on all manufacturer’s cartridges. The colored labels will also list the contaminants in abbreviation form to further help identify the types of hazards the cartridge has been approved for. Here are the abbreviations you will find on the labels:

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