Ethylene can trigger CO alarms

Coast Guard officers examining liquefied gas carriers along the Gulf Coast have learned ethylene, and other hydrocarbon vapors, can trigger carbon monoxide (CO) alarms on gas detectors before alarming for lower explosive limits. A May 30 safety alert warns the CO alarms – usually alerting to deadly engine combustion gases in confined spaces – can be an early warning of gas leaks before building to explosive levels. Coast Guard officials said Texas port control officers on one carrier thought their detectors were sniffing CO from combustion, but was a trigger from ethylene vapor coming from an 8-inch crack on a cargo vapor line. A marine chemist traced the problem, and told CG officials that the explosive level alarms likely did not occur because of high winds on deck. The molecular weight of ethylene is identical to CO, which would trigger that alarm. The detector’s manufacturer “confirmed that gases such as methane, propane, ethylene and mercaptan” will actuate the CO sensors before the lower explosive level alarms. (Source: Work Boat 05/30/18)