BY ROBERT A. FISCHER, RN, MSN
AN OXYGEN CYLINDER regulator spontaneously ignited and burned during a routine daily emergency medical system equipment check at a fire department. A firefighter suffered second-degree burns, and property damage was extensive.
The FDA has received 12 reports of oxygen cylinder regulators burning or exploding during emergency medical use or during routine equipment checks.
What went wrong?
After the fire described, the National Institute for Occupational Safety and Health (NIOSH) and the Center for Devices and Radiological Health at the FDA supported an extensive forensic analysis of oxygen cylinder regulators by an independent test lab. In its conclusion, the lab report stated that “any leakage [around damaged seals], especially slow weeping leaks, increases the probability of flow-friction ignition of this seal.” The FDA and NIOSH believe improper use of damaged gaskets/washers on the regulator was a major factor in both the ignition and severity of this fire.
Two types of washers are commonly used to enhance the seal at the cylinder valve/regulator interface. Many regulator manufacturers require a metal-bound elastomeric sealing washer that’s designed for multiple uses. The other common type is a plastic (usually nylon) crush gasket (CGA 870 seal) suitable for single use. The nylon crush gaskets require higher torque to seal the cylinder valve/regulator interface initially compared with the elastomeric sealing washers and require a progressively increasing torque to seal with each subsequent use. The cylinder valve/regulator connection is designed to be tightened by hand. But because increased torque is needed to seal it, someone might use a wrench or other hand tool to obtain the required seal; this could deform the crush gasket and damage the cylinder valve and regulator.
A deformed crush gasket or cylinder valve seat can let compressed oxygen leak past the cylinder valve seat across the nylon crush gasket, setting the stage for a fire. Oxygen itself isn’t flammable, but high-velocity oxygen flow impinging on the disrupted surface of the incorrectly seated or deformed washer produces enough friction (called flow friction) to heat up the washer—and, in the presence of 100% oxygen, to ignite the nylon crush gasket.
The same thing could happen with a metallic sealing washer, but the metallic sealing washers are less prone to leak, so paint or other nearby flammable objects are less likely to ignite.
What precautions can you take?
The FDA and NIOSH issued a joint Public Health Notification: Oxygen Regulator Fires Resulting from Incorrect Use of CGA 870 Seals April 24, 2006 and an update to the agencies’ recommendations on June 19, 2006. The PHN lists these precautions you can take to avoid explosions, cylinder ruptures, and fires from oxygen cylinder regulators:
- Before attaching regulators, always “crack” cylinder valves (open the valve just enough to let gas escape for a very short time) to expel foreign matter from the outlet port of the valve.
- Always follow the regulator manufacturer’s instructions for attaching the regulator to an oxygen cylinder.
- Always use the sealing gasket specified by the regulator manufacturer.
- Always inspect the regulator and CGA 870 seal before attaching it to the valve to ensure that the regulator is equipped with only one clean, sealing washer (reusable metal-bound rubber seal) or a new crush-type gasket (single use, not reusable, typically nylon) that’s in good condition.
- Always be certain the valve, regulator, and gasket are free from oil and grease contamination, which can contribute to ignition in oxygen systems.
- Tighten the T-handle firmly by hand; never use wrenches or other hand tools because they may over-torque the handle.
- Open the post valve slowly. If gas escapes at the juncture of the regulator and valve, quickly close the valve. Verify that the regulator is properly attached and the gasket is properly placed and in good condition.
If you have any questions or concerns, contact the biomedical department.
Although you need to support the adverse event–reporting policy of your health care facility, you may voluntarily report a medical device that doesn’t perform as intended by contacting MedWatch at 1-800-FDA-1088 (fax: 1-800-FDA-0178). Beverly Albrecht Gallauresi, RN, BS, MPH, who coordinates Device Safety, is a nurse-consultant at the Center for Devices and Radiological Health at the Food and Drug Administration in Rockville, Md.
Robert A. Fischer is a nurse-consultant at the Center for Devices and Radiological Health.
Nursing2007, Volume 37, Number 1 pg. 20