Magazine article Occupational Hazards

At Issue: Air Sampling Techniques

Magazine article Occupational Hazards

At Issue: Air Sampling Techniques

Article excerpt


San Francisco-based Bechtel National, an engineering and construction firm, had contracted to provide the National Aeronautical and Space Administration (NASA) with certain construction services at the Kennedy Space Center in Cape Canaveral, Fla. Bechtel was helping in the modification of NASA's mobile launch pad number three (MLP3), which is used in the assembly, transportation, and launch of space shuttles.

Each MLP has eight haunches, which serve as a support structure for the shuttle and solid rocket boosters. It is the work environment in the haunches, which extend into openings in the launch pad that facilitate the excape of the flame from the solid rocket boosters, from which alleged OSHA violations stemmed.

According to the case record, Bechtel received a complaint from a welder about smoke and dust in a haunch area. At about the same time, an employee complaint also was filed with OSHA concerning the working conditions in what was designated as a flame tunnel, though it was, in fact, a haunch area. An OSHA industrial hygienist investigated and Bechtel was subsequently cited by the agency for alleged violations of the following standards:

* 29 CFR 1926.55(a), which provides that "exposure of employees to inhalation, ingestion, skin absorption, or contact with any material or substance at a concentration above those specified in the 'Threshold Limit Values of Airborne Contaminants for 1970' of the American Conference of Governmental Industrial Hygienists, shall be avoided."

* 29 CFR 1926.353(b)(2), or 1926.353(b)(1) in the alternative. 1926.353(b)(2) provides that "when sufficient ventilation cannot be obtained without blocking the means of access, employees in the confined space shall be protected by air line respirators ... and an employee on the outside of such a confined space shall be assigned to maintain communication with those working within it and to aid them in an emergency." 1926.353(b)(1) provides that "... either general mechanical or local exhaust ventilation ... shall be provided whenever welding, cutting, or heating is performed in a confined space."

* 29 CFR 1926.21(b)(6)(i), which provides that "all employees required to enter into confined or enclosed spaces shall be instructed as to the nature of the hazards involved, the necessary precautions to be taken, and in the use of protective and emergency equipment required...."

No penalty was proposed. Bechtel contested the citations, and the case came before Administrative Law Judge James D. Burroughs.

The case record shows that on the OSHA industrial hygienist's first visit to the worksite, he observed the operation and talked with employees, some of whom told him that, while welding inside a haunch, smoke and gas was "real bad at times." The industrial hygienist and his supervisor decided to take air samples to determine gases generated and total particulate matter.

One employee was sampled to test for gaseous materials, but no excessive levels were detected. Another was sampled for toral particulates. A personal sampling pump was attached to his waist, a filter cassette was attached to the pump by a hose, and the filter cassette was attached to his shirt collar. Three different filters were used during a 315-minute sampling period, which showed an 8-hour time-weighted average of 24.5 mg/m.sup.3 -- above the allowable TLV of 15 Mg/M.sup.3.. These data triggered the citation for the alleged violation of 29 CFR 1926.55(a).

Although Bechtel did not dispute the weight of the filters nor the manner of computing the exposure level, the comany did argue that the sampling techniques the OSHA industrial hygienist uses resulted in skewed sample data, and that the employee was not exposed to levels of particulates exceeding permissible exposure levels. Bechtel based this argument on the contention that the filter cassettes were not placed inside the employee's welding hood, as sound practice would dictate, and that the industrial hygienist failed to calibrate the pumps at the worksite before and after taking the samples. …

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