Why measure butane?
The problem with butane isn?t so much that it’s toxic, but that it’s explosive at high concentrations. It may also be an indicator of problems that are occurring at the ConocoPhillips-Rodeo refinery if other chemicals are being released that may be more toxic than butane and that may not be measured by the monitors at the fenceline. The high alarm level set by the community is about one-tenth of what would be necessary to start a fire (1,000 parts per million, ppm), and the low alarm level (800 ppm) is set to provide an early warning that levels are increasing. The low alarm level has no health significance, but it is the ?safe? level used by the National Institute for Occupational Safety and Health (NIOSH). The primary risk of exposure to butane is narcosis, which occurs at high exposure levels. Exposure to 10,000 ppm butane for 10 minutes causes drowsiness, but there are no reports of systemic toxicity or irritation at this level (Gerarde 1963a, as cited in American Conference of Gov
