The Incident - An industrial research lab used arsine gas in
a semiconductor- related research project. It had been decided (appropriately in the joint
decision of the researcher and health and safety personnel) to use 100% arsine at 200 psig
cylinder pressure rather than a 10% arsine / hydrogen mixture which had a cylinder
pressure of over 2000 psig. The gas cabinet was equipped with normally-closed pneumatic
shutoff valves, a flow restrictor in the cylinder valve, and in-cabinet continuous
monitoring for arsine, in addition to other engineering controls. The side of the gas
cylinder received from the gas supplier was stenciled with the word "arsine."
The regulator had been chosen for 100% arsine gas. When the cylinder was connected to the
regulator assembly (with personnel using SCBA) and turned on, the guage needle immediately
pegged itself offscale on the regulator. The bourdon guage in the regulator burst and the
researcher headed for the door. In moving to the door he heard the sound of the pneumatic
valve closing. The gas detection system had immediately signaled for automatic shutdown of
the pneumatic valve. No arsine was detected in the lab area outside of the gas cabinet and
in-cabinet readings quickly dropped to zero. Subsequent examination of the cylinder
contents tag (attached to the cylinder neck) indicated the researcher had actually
received a 10% arsine mixture in hydrogen, at the elevated cylinder pressure of 2200 psig.
The researcher had not doubled checked the manufacturers identification tag and had relied
on the cylinder stenciling, which should not be considered reliable. Fortunately, the
engineering controls and personal protective equipment handled the situation effectively
Corrective Action - Research staff was informed to check the manufacturer’s
tag against their order information and not to rely on cylinder stencils. They were also
reminded to utilize engineering controls and protective equipment to minimize the impact
of highly hazardous materials incidents when the unexpected occurs.
