A system is provided for extinguishing accidental fires in paint spray booths of the type wherein oil is used as the medium for eliminating extraneous paint mist and overspray, said system providing control over both the oil and the medium used for extinguishing the fire. In such a spray booth, oil from a self-contained reservoir located at the bottom of the booth is circulated over a plurality of baffles within the booth. Paint mist is drawn by flow of air into contact with the oil covered baffles, and the paint solids are thereby entrained in the oil and collected in the oil reservoir. An appropriate fire extinguishing system for such spray booth comprises a plurality of water fog nozzles within the booth that are activated in response to a fire, and which therefore discharge water into the reservoir. Pursuant to the invention, means are provided to control and preserve the oil which is displaced by water accumulating in the oil reservoir, to maximize fire-fighting efficiency, and to discharge excess water from the booth while safely retaining the oil.