07/10//2006 Fires Possible When Cylinder Seals Misused

NIOSH and the FDA have issued a joint release warning users of fire danger when CGA 870 seals are used incorrectly on oxygen cylinders.

The FDA has received a dozen reports of regulators used with oxygen cylinders burning or exploding, in some cases injuring emergency personnel.  The organizations believe improper use of gaskets/washers in these regulators was a major factor, although other factors likely contributed as well.

Two types of washers, called CGA 870 seals, are commonly used to seal the cylinder valve/regulator interface: One, required by many regulator manufacturers, is a metal-bound elastromeric sealing washer; the other, often supplied with refilled oxygen cylinders, is a plastic crush gasket for single use.

The latter require higher torque than the former to seal the interface – and if they are reused, they require more torque with each successive use.  This may necessitate using a wrench or hand tool.  However, as the connection is designed to be hand-tightened, this can deform the gasket and damage the valve and regulator.  This may result in oxygen leaking past the cylinder valve seat and across the crush gasket.   Forensic analysis has shown that “flow friction” caused by this leakage may produce enough thermal energy to spontaneously ignite the gasket material.

The FDA and NIOSH recommend that plastic crush gaskets never be reused.  For their full release, see whttp://www.fda.gov/cdrh/safety/042406-o2fires.html.  They also ask users owho have experienced this phenomenon to notify them through the reporting program MedWatch at 800/FDA-1088 or https://www.accessdata.fda.gov/scripts/medwatch/medwatch-online.htm.