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OSHA Hazard Information Bulletins
Potential Hazard in Use of Water Spray for Preventing or Controlling the Ignition of Flammable Atmospheres
May 1, 1986
MEMORANDUM FOR REGIONAL ADMINISTRATORS
The National Institute for Occupational Safety and Health (NIOSH) has investigated a potentially serious safety hazard involving the common use of water spray to control fires involving flammable gas of vapor. Under certain conditions, the use of water spray may actually increase the severity of fires and explosions.
NIOSH reports that the use of water spray or fog patterns to prevent ignition or to control flame propagation when dealing with flammable materials could be extremely dangerous. For example, an accident occurred when a rescue team attempted to gain access to a recently-emptied toluene tank by sawing an opening in the side of the tank. The area which was being cut was blanketed with water fog both inside and outside the tank. Still, an explosion occurred which killed one person and injured 15 others.
The use of water spray has evolved because of (a) the traditional use of water in firefighting, (b) the belief that water sprays provide critical ventilation, (c) the ready availability of water spray, and (d) the proven effectiveness of water sprays in controlling some of the hazards of flammable materials.
Failure of the hose on a fire extinguisher renders it inoperable and may cause injury to the user. The OSHA 29 CFR 1910.157 standards on portable fire extinguishers are directly applicable in this instance, especially 1910.157(c)(4) which mandates that extinguishers be maintained in a fully charged and operable condition, and 1910.157(f) which outlines requirements for hydrostatic testing of extinguishers.
We recommend that compliance and consultation personnel be made aware of the hazards addressed in this bulletin. Please disseminate this information to Area Offices, State Plan States, and Consultation Project Offices.