In comparison with other hazards of anesthesia, fires and explosions occur very infrequently because of precautions for their prevention so that they are relatively insignificant. The authors had experience of a case of explosion with fire in an oxygen delivery tube and the wrapping cloth of the oxygen cylinder. A piece of plaster used for prevention of leakage from the oxygen delivery tube occluded the filter in a pin-index system of an anesthesia machine. It is suspected that adiabatic compression may produce a momentary temperature of over 900 ℃ in an occluding part, thus igniting minute particles detached by the gas stream from the walls of the oxygen delivery tube. In case of malfunctioning in anesthetic apparatus, it should be repaired only by expert engineers.