Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at

JUN 4 1990

U.S. Department of Labor
Occupational Safety
and Health Administration
Washington, D.C. 20210

Reply to the Attention of:

JUN 4, 1990



THRU:                  LEO CAREY Director Office of Field Program

FROM:                  THOMAS J. SHEPICH Director Directorate of Technical

SUBJECT:               Use of Chemical Cartridge Respirators

On February 26, the National Institute for Occupational Safety and Health (NIOSH) distributed a "Respirator Information Notice on Chemical Cartridge Respirators" which stated that since OSHA has revised the permissible exposure limits (PEL) for toxic air contaminants listed in Table Z of 1910.1000, NIOSH has decided to eliminate the maximum use concentrations (MUC) labeling requirement for all approved chemical cartridges under the provision of [42 CFR 84.257] (copies attached).

[This document was edited on 03/30/99 to strike information that no longer reflects current OSHA policy.]

The NIOSH notice has also eliminated the labeling requirements on cartridges for protection against the exposure to organic vapors. We have received numerous inquiries concerning this issue. Since OSHA does not have specific standards for the majority of organic compounds listed in Table Z of 1910.1000, the elimination of the MUC may cause overexposure because many of these contaminants have inadequate odor warning properties. In order to ensure that the organic vapor cartridges are used properly, the attached guidelines should answer most questions when you receive inquiries concerning this issue.







1. Use Limitation:

Use of the cartridges is limited to the lowest of the three air contaminant concentrations determined by the following:

a. Immediately dangerous to life or health (IDLH) concentration.

b. 1,000 parts per million (ppm).

c. The maximum use limit (MUL) which is 10 times the OSHA permissible exposure limit (PEL).

2. These organic vapor cartridges are approved for respiratory protection against organic vapors with definite odor warning properties, meaning that the air contaminant must have a distinctive odor at concentrations at or below the permissible exposure limit established by OSHA for the air contaminant, and the odor warning properties are not affected by olfactory fatigue.

3. The use of chemical cartridges for protection against an air contaminant without definite odor warning properties is acceptable only when the use is permitted in specific OSHA health standards (such as acrylonitrile), when the cartridge has an approved end- of-service-life indicator (such as mercury), or when the cartridge breakthrough time is available based on the following test conditions:

a. Challenge concentration: 10 times the PEL.

b. Air Flow: 32 liters per minute continuously.

c. Relative humidity: 85 to 90%.

d. Temperature: 20 to 25 degree Celsius.

The breakthrough time should be calculated as the mean of at least three samples at a 95% confidence level. Unless the cartridge desorption information indicates that there is no significant desorption from overnight storage, the cartridge should be replaced at the beginning of each shift or prior to the experimental breakthrough time, whichever comes first.




4. Many respirator manufacturers have a list of air contaminants for which the use of chemical cartridges for respiratory protection is not recommended regardless of concentration and time of exposure. Some examples are:

Acrolein, aniline, arsine, bromine, carbon disulfide, carbon monoxide, dimethyl aniline, dimethyl sulfate, hydrogen cyanide, hydrogen fluoride, hydrogen selenide, hydrogen sulfide, methanol, methyl bromide, methyl chloride, isocyanates (MDI, TDI, etc.), nickel carbonyl, nitrobenzene, nitrogen oxides, nitroglycerine, nitromethane, ozone, phosgene, phosphine, phosphorous trichloride, stibine, and vinyl chloride.

The manufacturer's recommendation should be closely followed for chemical cartridge selection. Since the above list is not complete, consult with the respirator manufacturer for additional information.

Public Health Service
Centers for Disease Control
National Institute for
Occupational Safety and Health - ALOSH
944 Chestnut Ridge Road
Morgantown, WV 26505-2888










February 26, 1990



In 1972, the National Institute for Occupational Safety and Health (NIOSH) and the Bureau of Mines (BOM) initiated the respirator certification program conducted under Part 11 of Title 30 Code of Federal Regulations (30 CFR Part 11). Currently, NIOSH and the Mine Safety and Health Administration (MSHA) jointly certify respirators that meet the requirements of 30 CFR Part 11. These regulations provide a description of chemical cartridge respirators that include maximum use concentrations (MUCs) for certified cartridges (Section 11.150). These maximum use concentrations are based on the acceptable exposure limits at the time 30 CFR Part 11 was promulgated. They were calculated by multiplying the assigned protection factor of 10 for half mask chemical cartridge respirators by the exposure limit accepted in 1972 for each specific contaminant. Although not specifically required in 30 CFR Part 11, NIOSH has included these maximum use concentrations on all chemical cartridge approval labels.

OSHA recently revised the permissible exposure limits (PELs) for 212 substances and established permissible exposure limits for an additional 164 substances (Air Contaminants Standard, 29 CFR 1910.1000). The revised permissible exposure limits affect the maximum use concentrations for three of the substances listed in 30 CFR Part 11 (ammonia, chlorine, and sulfur dioxide). Compliance with the new permissible exposure limits became mandatory on September 1, 1989. Other regulatory agencies have established exposure limits that vary from the new OSHA permissible exposure limits. Future standards may further revise acceptable exposure limits. Thus, NIOSH has decided to eliminate maximum use concentrations from chemical cartridge approval letters and labels. NIOSH has sent a letter to all manufacturers of MSHA/NIOSH-certified chemical cartridge respirators requesting a modification to approval labels and user instructions. However, respirator and cartridge labels and instructions with the old maximum use concentrations are already in use. Therefore, NIOSH is advising that all users of chemical cartridge respirators of the change in maximum use concentrations.

The following table lists substances for which OSHA does not have specific substance standards and for which NIOSH has specifically certified chemical cartridges. This table only applies to respirator users who are covered by OSHA regulations.

     Type of chemical Cartridge respirator(7)       |    Maximum
                                                    |    Use
                                                    |    Concentration,
                                                    |    parts per million
Ammonia.............................................|                300
Chlorine............................................|                10
Hydrogen chloride...................................|                50
Methyl amine........................................|                100
Organic Vapor.......................................|             (H)1,000
Sulfur dioxide......................................|                50
Vinyl Chloride......................................|                10

(7)Not for use against gases or vapors with poor warning properties (except where MSHA or Occupational Safety and Health Administration standards may permit such use for a specific gas or vapor) or those which generate high heats of reaction with sorbent material in the cartridge.

(H)Maximum use concentrations are lower for organic vapors which produce atmospheres immediately hazardous to life or health at concentrations equal to or lower than this concentration.

NOTE: Chemical cartridge respirators for respiratory protection against gases or vapors, which are not specifically listed with their maximum use concentration except pesticides, may be approved if the applicant submits a request for such approval in writing, to the Institute. MSHA and the Institute shall consider each such application and accept or reject the application after a review of the effect on the wearer's health and safety and in the light of any field experience in use of chemical cartridge respirators as protection against such hazards.