filling Stations 34 and 28. At Station 28, the readings were taken with an oxygen analyzer supplied by the independent medical service while at Station 34 the readings were taken with the station’s oxygen analyzer. The oxygen purity readings for both stations were 99.7% pure oxygen. Random samples taken from cylinders in the field also proved sufficient.
The fire fighters involved in the process of filling cylinders with oxygen are trained in the proper procedures. The oxygen cylinders commonly filled by the fire department and used as medical equipment by the paramedics and EMTs are D- and E-size cylinders (Photo 3). These cylinders are filled from a cascade system of 12 M-size (300-cubic-ft.) cylinders connected in series (Photo 4). The cascade systems used at Station 34 and 28 are capable of refilling 14 D- or E-size oxygen cylinders at a time. Two banks of 7 cylinders each are arranged in a storage rack for filling (Photo 5). As cylinders are refilled, 1 out of every 14 is sampled to ensure the cylinder is filled with 99.7% pure oxygen. If a sample is found to fall below 99.7%, the entire lot of 14 is isolated until the problem is identified and corrected. After filling, each cylinder is capped with a plastic plug over the post valve opening to keep the valve clean and to identify cylinders that are ready for use.
The fire department’s standard procedure requires at least 300 psi of pressure to remain in the cylinders awaiting to be filled. If cylinder pressure is less than 300 psi, the cylinder is taken out of service, flushed with nitrogen using compressed nitrogen from a size M cylinder and a Model DOA-V192-AA gas pump, and returned to the vender for hydrostatic testing and inspection. Standard procedures also require the cascade operator to check the hydrostatic date of each cylinder before it is refilled. Steel and aluminum cylinders must be inspected and hydrostatically retested every 5 years per U.S. Department of Transportation regulation Title 49, Code of Federal Regulation (CFR) Part 173.34 (e).[1]
A representative from the fire department stated that the oxygen resuscitator involved in the incident was pressure checked by a fire fighter on the earlier shift, and the resuscitator appeared to be working properly. The department also stated that the oxygen resuscitator was not used for patient care during the shift prior to the incident.
The representative from the fire department stated that it had previously experienced an incident with an oxygen cylinder and regulator of the same type involved in this investigation. Although the incident did not cause serious injury, the fire department replaced all of its cylinder regulators with a different model from a new manufacturer. After the regulators were changed out, the fire department received a notice from the manufacturer of the previous regulators stating that the regulator had been associated with fire in six incidents reported over the past 3 years. The manufacturer notice indicated that a retrofit kit would be forwarded to the fire department upon request. The retrofit kit included a bronze sintered-inlet filter, a new warning label, an allen wrench, and an instruction sheet necessary to retrofit the existing regulator. The fire department’s previously used regulators were listed in the notice so the fire department notified the manufacturer, who supplied the department with retrofit kits for all of the previous regulators. The fire department retrofitted all of it’s regulators but did not put them back into service. Even though these regulators were not put back into service, the regulator involved in the incident (which was retrofitted) was mistakenly placed into service during a maintenance changeover.
In addition to the replacement parts, the retrofit kit contained a warning sticker that was to be placed on each regulator as soon as it had been retrofitted (Photo 6). The sticker read: WARNING: 1. The introduction of contaminates and hydrocarbon substances into the regulator may cause combustion; 2. Open the cylinder post valve slowly. The sudden inrush of oxygen into the regulator may cause combustion if contaminates are present. The sticker served not only as a warning but also as an identifier to indicate regulators that had been retrofitted. A retrofit sticker had been placed on the regulator involved in this incident. After the incident, the fire department sent the cylinder and regulator involved in the incident to an independent testing laboratory for further testing. Oxygen resuscitators are medical devices which come under the jurisdiction of the Food and Drug Administration (FDA). NIOSH has been working with the FDA on the issues identified through the NIOSH investigation. The FDA recently issued a Public Health Advisory jointly with NIOSH entitled Explosions and Fires in Aluminum Oxygen Regulators. A copy of this advisory is available on the FDA homepage at: www.fda.gov/cdrh/safety.html.
INDEPENDENT TEST RESULTS
The results reported here are from the tests and the report completed by Barry Newton, B.S.M.E., P.E.2 at the request of the fire department. The results concluded the regulator was retrofitted with the new parts supplied by
- ↑ Title 49, Code of Federal Regulations (CFR) Part 173.34 (e), Qualification, maintenance, and use of cylinders. U.S. Department of Transportation (DOT).
