A recent Review Commission ALJ decision[1] vacating an OSHA citation could simply be viewed as one where OSHA failed to carry its burden of proof, but it might better be viewed as a reminder of a fire hazard that may not be adequately addressed by some facilities in properly storing, handling and using oxygen cylinders.

During an inspection of a construction project at a medical center, the OSHA inspector found a 2-compartment cage built by the welding contractor with at least ten liquid petroleum cylinders in the left compartment and two oxygen cylinders in the right compartment. The two compartments were separated by two 1/8-inch steel barriers separated from each other by 2 inches of air. Both barriers were taller than 5 feet. OSHA cited the welding contractor for an alleged violation of the OSHA welding standard for construction, 29 C.F.R. § 1926.350(a)(10), which states:

Oxygen cylinders in storage shall be separated from fuel-gas cylinders or combustible materials (especially oil or grease), a minimum distance of 20 feet (6.1 m) or by a noncombustible barrier at least 5 feet (1.5 m) high having a fire-resistance rating of at least one-half hour.

Under well-established case law, to sustain a violation, OSHA must establish the following elements by a preponderance of the evidence: (1) the cited standard applies to the facts; (2) the requirements of the standard were not met; (3) employees had access to the hazardous condition; and (4) the employer knew or could have known of the hazardous condition with the exercise of reasonable diligence. There was no dispute with respect to the issues of employee access (element 3) or employer knowledge (element 4). There was a dispute as to whether the standard applied (i.e., whether the cylinders were “in storage”) and, if so, whether there was non-compliance (i.e., whether the steel barriers had a fire-resistance rating of at least one-half hour.)

It is important to note that OSHA’s General Industry standard for welding, 29 CFR 1910.253(b)(4)(iii),[2] contains language identical to the cited construction standard, but, due to additional language in related sections of the General Industry standard, is given a different interpretation. Oxygen cylinders in general industry workplaces are not considered to be “in storage” when they are either "in use" or "connected for use". However, in the construction industry, an oxygen cylinder is considered to be in use only when gas is being drawn or it is reasonably anticipated that gas will be drawn from the cylinder within 24 hours.[3]

OSHA’s longstanding position is that “whether it is ‘reasonably anticipated’” that gas will be drawn within 24 hours is based on whether specific welding or cutting work is planned for that period and the number of gas cylinders expected to be required to do that work.” The judge held that OSHA had the burden of proof on this issue and did not produced any evidence regarding the welding contractors intended use of the cylinders within the relevant twenty-four hour period. In contrast, the hearing record showed that the welding contractor was performing welding activities daily and the cage was accessed as needed throughout the day. Based on the record, the judge held that it was reasonably anticipated that gas would be drawn from the cylinder during the next 24 hours, and therefore, the cylinders were not considered to be in storage, and the cited standard did not apply.

While the judge could have vacated the citation on that ground, he went on to hold that, even if the cited standard did apply, OSHA had not demonstrated that the barrier between the two compartments had a fire-resistance rating of less than one-half hour. According to the judge, the parties conceded the barriers were “made of noncombustible steel, and … exceeded the 5-foot tall requirement.” OSHA asserted that it did not need to test or otherwise analyze the fire resistance of the barriers in the welding contractors cage, but could rely on the following excerpt from an internal OSHA “interpretative guidance” memorandum (the June 30, 2006, Memorandum on Interpretation for Fire Resistance Ratings for Metal) stating that a 1/2-inch thick solid steel barrier would not provide at least 1/2-hour fire resistance:

In fact, a solid mild steel plate barrier, ½-inch thick, would fail to meet the fire-resistance rating for ½-hour (see attached memorandum, dated July 15, 1982). To obtain a ½-hour fire-resistance rating criteria, the most common materials used are plaster (cement, lime, and perlite) fillers, and mineral wool fillers. For example, a fire barrier (solid partition) would be comprised of metal lath on ¾-inch steel channels, combined with a 2-inch thick cement plaster (see attached notes titled, 1910.253- Welding, Cutting and Brazing). Solid mild steel plate barriers combined with plaster fillers such as concrete provide a higher protection factor that meet or exceed the ½-hour fire-resistance rating, because concrete has low thermal conductivity and capacity properties.

Based on the above information, solid mild steel plate barriers, ½-inch thick, used alone would not meet OSHA’s ½-hour requirements. However, a combination of materials used in conjunction with solid mild steel plate barriers would achieve the ½-hour fire-resistance rating criteria. Therefore, any material used that meets or exceeds the ½-hour fire-resistance rating would be in compliance and acceptable for 29 CFR 1910.253(b)(4)(iii).

OSHA asserted that if a 1/2-inch thick solid steel barrier was inadequate, then the 1/4-inch barrier used by the welding contractor did not provide the appropriate fire resistance. The judge found no merit in this argument and indicated that OSHA would need to provide a fire-resistance analysis for the barrier based on a testing protocol validated by a professional engineer.

In a previous Review Commission ALJ decision addressing the same issue,[4] another the judge took the opposite view and accepted the June 30, 2006 OSHA memorandum as adequate evidence to establish that a ¼ inch steel barrier was inadequate. The judge also upheld the citation on the alternative ground that there were one inch gaps between each end of the steel barrier and the frame of the rack so that the barrier was inadequate.

In both cases, the fire resistance rating of the barrier was unknown. Neither OSHA nor the employer tested the barrier to determine its fire resistance rating or otherwise ascertained that it met the fire resistance rating required by the standard. Although OSHA has the burden of proof to establish a violation (i.e., that the barrier does not have a fire-resistance rating of at least one-half hour), the employer also has the obligation to test or otherwise ascertain that the barrier does have the required fire-resistance rating.

On a related note, although steel may be generally viewed as noncombustible, it can burn under certain conditions in the presence of high-pressure oxygen. There was a fairly recent incident in which high-pressure oxygen was introduced into a stainless-steel manifold containing room air and apparently, some dust particles, and a purge valve was opened at the same time to purge any contaminants from the piping. There was an ignition in the main isolation valve of the regulator on the manifold that resulted in a flash fire that consumed a portion of the stainless-steel regulator and the manifold. The most plausible explanation for the event is that there was small amount of combustible material in the piping that was ignited by the high velocity impact of the particles on the wall of the piping and the heat generated by the adiabtic compression of the oxygen, and that the heat of that combustion was sufficient to ignite the stainless steel. Because stainless steel supports combustion, the recognized standards for oxygen piping systems recommend the use of burn-resistant alloys of copper (e.g., brass) or nickel for high-pressure oxygen systems. One standard indicates that, depending on composition, the use of stainless steel requires oxygen velocity limitations at pressures as low as 200 psig and that all stainless steel requires oxygen velocity limitations at pressures above 375 psig.[5]