What happened? A size 7 cylinder (6" diameter x 15" height) of carbon monoxide (CO), 30 ft3 capacity (under filled to a capacity of 15 ft3) with a 0.006 in. restrictive flow orifice completely leaked out in the fume hood.
Watch video clip (Windows Media Player is required).
Why did it happen? There was a leak between the regulator and the flow control valve (see video of a soap bubble leak check). A user apparently opened the cylinder valve and flow control valve to use the gas and only closed the flow control valve when done with the gas allowing the gas to escape through the leak. Fortunately, the leak was contained in an operating fume hood.
Carbon monoxide (PDF format) is a toxic and flammable gas that can cause illness, permanent neurological damage, and death. Because it is colorless, odorless, and nonirritating, CO can overcome exposed persons without warning. Often there is little time before they experience symptoms that inhibit their ability to seek safety.
How can a similar occurrence be avoided? Toxic gas systems must be leak checked (using the soap bubble method at a minimum). Cylinder valves must closed when cylinders are not in use. It is also advisable to use an instrument to give warning of the presence of toxic concentrations - especially with toxic gases having poor warning properties (i.e., odor or irritation), such as carbon monoxide.
Carbon monoxide is an extremely hazardous chemical that requires prior approval (Chemical Safety Level 3 or CSL-3) by the Institutional Chemical Safety Committee (ICSC). For approval, the Minimum Requirements for Toxic/Corrosive Gas Use (PDF format) will at least be required by the ICSC.
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