During the 1990s, former Boston firefighter and researcher Charles Kenney discovered that a highly flammable gas refrigerant, methyl chloride, had been used as a substitute for freon, which was in short wartime supply. Kenney reported that floor plans, but not the fire investigation report, showed air-conditioning condenser units near street level on the other side of a non-structural wall from the Melody Lounge, and that these units had been serviced since the start of the war. Kenney also reported that photographic evidence indicates an origin for the fire in the wall behind the palm tree and suggested ignition of methyl chloride accelerant by an electrical failure caused by substandard wiring. Methyl chloride combustion is consistent with some aspects of the fire (reported flame colors, smell and inhalation symptoms) but requires additional explanation for ceiling-level fire as the gas is 1.7 times as dense as air.