Standard Interpretations - Table of Contents|
| Standard Number:||1910.134(d)(3)(iii); 1910.134(d)(1)(i)|
July 18, 2000
Mr. Larry Janssen, CIH
Dear Mr. Janssen:
Thank you for your December 10, 1999 letter to the Occupational Safety and Health Administration's (OSHA's) Directorate of Compliance Programs (DCP). You requested clarification regarding OSHA's position on the selection of air purifying respirators (APRs) for gases and vapors with poor warning properties, particularly the common diisocyanates such as Toluene-2,4-diisocyanate (TDI), Hexamethylene-1,6-diisocyanate (HDI) and Methylene bisphenyl isocyanate (MDI). We apologize for the delay in this response.
The Preamble to the revised standard points out that there is a great variation between individuals in their sensory detection of chemicals and most toxic substances do not have appropriate sensory warning properties. The standard no longer permits the use of warning properties as the sole basis for determining that an air-purifying respirator affords adequate protection against exposures to vapors and gases. For atmospheres which are not Immediately Dangerous to Life or Health (IDLH), APRs are now considered acceptable as long as appropriate precautions and change out schedules are in place, even for use against substances with poor warning properties.
Paragraph 1910.134(d)(1)(i) of the revised Respiratory Protection Standard states "the employer shall select and provide an appropriate respirator based on the respiratory hazard(s) to which the worker is exposed and the workplace and user factors that affect respirator performance and reliability."
Paragraph(d)(3)(iii) further states that for protection against gases and vapors an air-purifying respirator may be used provided that:
(1) The respirator is equipped with an end-of-service life indicator (ESLI) certified by NIOSH for the contaminant; or
(2) If there is no ESLI appropriate for conditions in the workplace, the employer implements a change schedule for canisters and cartridges that is based on objective data that will ensure that canisters and cartridges are changed before the end of their service life. The employer shall describe in the respirator program the information and data relied upon and the basis for the change schedule and the basis for reliance on the data.
Currently, there are few respirators available on the market with end-of-service life indicators (ESLI), and none for MDI. An employer must select a cartridge or canister recommended for that chemical by the manufacturer. The employer must then implement a change schedule for the canister or cartridges that is based on objective information or data that will ensure that the canister and cartridges are changed before the end of their service life. The data relied upon and the information forming the basis of the determination must be included in the written respirator program. If more information becomes available, an employer would be expected to review and if necessary, revise the change out schedule.
The employer is required to select the appropriate respirator for each situation. Some factors that should be included in the evaluation by the employer are:
We anticipate that some employers who perform the required evaluation will determine that APRs are appropriate for their circumstances. Others may prefer to provide powered-air purifying respirators (PAPRs). Under some circumstances, other employers may determine that SARs may be the only appropriate type of respirator for these hazards. As with any other situation requiring the use of respirators, an effective written respiratory protection program must be developed and implemented. Key provisions include fit testing, medical evaluations, proper use of respirators, training and information (including the need for a user seal check each time the respirator is donned), maintenance and care of respirators, program evaluation and recordkeeping.
You also noted that the OSHA website contains six letters of interpretation which predate the revision to the respiratory protection standard as well as statements on the "Isocyanates" Technical Links page which reflect that diisocyanates have poor warning properties, are sensitizers, or are too hazardous to allow air purifying respirators. OSHA is currently reviewing all letters on our website for inconsistencies with OSHA policy and appropriate action for these letters will be taken.
Thank you for your interest in occupational safety and health. We hope you find this information helpful. Please be aware that OSHA's enforcement guidance is subject to periodic review and clarification, amplification, or correction. Such guidance could also be affected by subsequent rulemaking. In the future, should you wish to verify that the guidance provided herein remains current, you may consult OSHA's website at http://www.osha.gov. If you have further questions please feel free to call OSHA's Office of Health Compliance Assistance at (202) 693-2190.
Richard E. Fairfax, Director
Standard Interpretations - Table of Contents|