[abstract] THE RISK OF STATIC SPARK IGNITION IN ENRICHED OXYGEN ENVIRONMENTS

Abstract

BACKGROUND: Sparks resulting from the discharge of accumulated static electrical charges have been identified as ignition sources in many environments. Materials exposed to enriched oxygen environments exhibit lower ignition energies and more rapid combustion. Static electrical charges accumulated by humans have been measured as high as 18,000 volts, resulting in calculated discharge energies on the order of 50 - 60 millijoules. There is limited data available concerning the spark ignition energies of materials other than gases or vapors, excepting a series of studies conducted in the late 1950's and early 1960's which were sparked by concerns over static-caused fires in oxygen tents. REVIEW: Materials studied were textile and plastic materials typically found in or around oxygen tents. Using spark energies ranging from 20 - 800 mj, no single sparks were found to cause ignitions in clean materials regardless of oxygen concentration, though ignitions did occur following multiple sparks (as rapid as 60 sparks/sec. x 30 sec.) in 100percent oxygen environments. Materials contaminated with petrolatum exhibited ignitions following multiple spark energy levels as low as 25 mj in 64percent oxygen. A primary determinate of ignition appears to be the inherent flammability of the material studied. CONCLUSION: If materials introduced into enriched oxygen environments cannot be controlled, measures to control static charge development can be implemented. Measures to control static are primarily focused on prevention of charge accumulation by providing low resistance paths to ground either through increasing relative humidity or various grounding systems.