What happened? Small carbon monoxide (CO) leaks were detected during a Chemical Safety Level 3 (CSL-3) prior approval review (see photos below). CO levels at the leaks were greater than several hundred ppm. CO levels in the well ventilated lab were 2 -3 ppm. The recommended exposure limit for CO is 25 ppm, as an 8-hour, time-weighted average (TWA).
While the leaks were not significant from an occupant exposure standpoint, they were a warning of greater possible risks. 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.
Why did it happen? CO was plumbed outside of an exhausted enclosure with inappropriate plumbing (a conglomeration of plastic tubing, hose clamps, compression fittings, irrigation plumbing parts, copper pipe, valves, flow meters, filters, etc.) and used in a furnace without an exhausted enclosure. Several other major safety deficiencies were also noted in the review (see photo descriptions).
How can a similar occurrence be avoided? 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, which includes welded, threaded or flanged (e.g., VCR fittings) connections throughout unless an appropriate exhausted enclosure is provided.
 |
 |
Above Left – Source CO gas in a required exhausted enclosure (i.e., fume hood). However, the fume hood does not have the required airflow measuring device and visual and audible alarms
Above Right – "Empty" CO cylinders stored outside of an exhausted enclosure. They must be stored like "Full" cylinders – in an exhausted enclosure.
Below Left – Inappropriate CO plumbing and furnace outside of an exhausted enclosure. The furnaces (x2), valves, fittings, filters, flow meters, etc., must be in an exhausted enclosure and connected to the source gas by a continuous metal pipe. Note the home CO detector hanging from the CO2 gas cylinder, which is not appropriate for compressed CO gas use because of poor sensitivity, slow response time and it can't be calibrated. The CO detector was reading zero ppm. Since the gas use in this lab can go on for up to 30 days at a time, often unattended, a calibrated, industrial gas detector connected to a solenoid valve at the gas source is warranted. The required exhaust airflow measuring device should also be connected to the solenoid valve. Gas detection or loss of exhaust airflow would stop the flow of gas.
Below Right – Yellow arrows indicate the CO leak locations on the plumbing and furnace.
 |
 |
All contents copyright © 2008. Arizona Board of Regents.