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 https://www.osha.gov.

May 17, 1988

  Office of Variance Determination
  Office of Construction and Maritime
  Compliance Assistance
SUBJECT: Use of Oxygen for Decompression Underground
  Tunnel Workers

You have requested our review of your draft on the above subject.

It is our understanding that oxygen in 100 percent concentration can produce pulmonary and central nervous system problems. However, these medical problems in the use of high oxygen concentration at greater that normal pressures, would be for OSHA physicians to answer.

The potential danger of fire in the use of oxygen is well known. It has been found that even a modest oxygen enrichment of the atmosphere can greatly increase burning rates of common combustibles. In 100 percent O(2), slow burning materials are consumed explosively. Fires in compressed air atmospheres are more intense than at ordinary pressures. Therefore, due to this inherent fire and explosive hazard involved with the use of compressed air and O(2), we are very concerned about the hazards to which tunnel workers will be exposed.

Attached, Please find some change in your proposed rules.

Your No. 17, page 6, may be in conflict with 29 CFR 1926.803(b)(1):

(b) Medical attendance, examination, and regulations. (1) there shall be retained one or more licensed physicians familiar with and experienced in the medical aspects of compressed air work and the treatment of decompression illness. He shall be available at all times while work is in progress in order to provide medical supervision of employees employed in compressed air work. He shall himself be physically qualified and be willing to enter a pressurized environment.

You may wish to review.

A number of meetings have been held with you and your staff where background information has been discussed and furnished to you. I feel we must weigh, not only the specific hazard addressed, but what is the potential, or related hazards this approach can create.

At out last meeting in my office the question of a Region V letter to you was addressed (copy attached).

Engineering research has established that the "only" use of O(2) decompression was, in San Paulo, Brazil back in 1976. We have evidence that O(2) has not been used for decompression of tunnel workers in Hong Kong or elsewhere. In fact, Hong Kong government authorities - would not approve its use. The United Kingdom, as we, only allow the use of O(2) at the medical lock - for O(2) treatment of the workers in case of emergency.

Please advise it we can be of further assistance.