Respirator Categories Based on Filter Efficiency and Oil Resistance

Taken from Pesticide Registration Notice (PRN) 98-9 Notice to Manufacturers, Producers, Formulators and Registrants of Agricultural Pesticides.

Three categories exist for filter efficiency and each category has three possible oil degradation resistances that may be selected and matched with filter efficiency. Each of the nine resulting respirator categories is designated by a code in which a letter -- N, R or P -- represents its oil resistance and a number -- 95, 99 or 100 -- represents filter efficiency.

  • 95%
  • 99%
  • 99.97%

The three categories of oil degradation resistance are based on the degree to which the filter performance is impaired by the deposition of oil. Examples of oils include: di-octyl phthalate oil, glycerine, and hydrocarbons used as lubricants. For Part 84 respirators, di-octyl phthalate (DOP) oil is utilized as a challenge material; this substance will act to neutralize the electrostatic charges present on the surface of filter fibers and reduce respirator efficiency. In this document the term "oil" will be used to represent any high-boiling point liquid hydrocarbon that will accumulate on the particulate filter of a respirator with minimal evaporation. Note that the accumulation of oil may lead to filter efficiency degradation. In assessing formulated products, registrants should work closely with respirator manufacturers to assure that the proper filter type is selected for the product.

  • N-series (not resistant to oil) particulate filters may be used for solid particulate or liquid particulate hazards. During certification sodium chloride is used as a testing material and a very high particulate load (200 mg) is utilized for the test. Given the rigorousness of the testing regime, there is no recommended time limitation for an N-series filter.
  • R-series (oil resistant) particulate filters may be used for solid and liquid particulate hazards. For those products containing oil, the R-series is to be used for only one work shift (an 8 hour work period) or per manufacturer's recommendations.
  • P-series filters may be used for more than a single work period, but NIOSH has requested each respirator manufacturer to establish service time recommendations as part of their user instructions. It has been determined that long term oil exposure could reduce the efficiency of a P100 filter to levels below that of a P95 filter.

Respirator Category Chart


Filter Efficiency
Oil Resistance
N-series particulate filters
Not resistant to oil.
R-series particulate filters
Oil-resistant.

P-series filters
Oil-proof.
95% N95

Not resistant to oil.

May be used for solid particulate or liquid particulate hazards.

No time limitations
Moderate filter efficiency.

R95

Oil-resistant.

May be used for solid and liquid particulate hazards.

Time limitation: 8 hours or manufacturer recommendation.

Moderate filter efficiency.

P95

Oil-proof.

Time limitation: manufacturer recommendation, usually more than 8 hours.

Moderate filter efficiency.

99% N99

Not resistant to oil.

May be used for solid particulate or liquid particulate hazards.

No time limitations.

High filter efficiency.

R99

Oil-resistant.

May be used for solid and liquid particulate hazards.

Time limitation: 8 hours or manufacturer recommendation.

High filter efficiency.

P99

Oil-proof.

Time limitation: manufacturer recommendation, usually more than 8 hours.

High filter efficiency.

99.97% N100

Not resistant to oil.

May be used for solid particulate or liquid particulate hazards.

No time limitations.

Very high filter efficiency.

R100

Oil-resistant.

May be used for solid and liquid particulate hazards.

Time limitation: 8 hours or manufacturer recommendation.

Very high filter efficiency.

P100

Oil-proof.

Time limitation: manufacturer recommendation, usually more than 8 hours.

Very high filter efficiency.
NOTE: long-term exposure to oil can lower efficiency to 95%.


View the Federal Register Policy Statement on Labeling Requirements for Pesticides; Respirator Compliance:     Federal Register: May 7, 1998 (Volume 63, Number 88)

PR Notice 98-9 Notice to Manufacturers, Producers, Formulators and Registrants of Agricultural Pesticides--Subject: Modification of Respirator Statements for Pesticide Product Labels. View the entire PRN. (PDF format)