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Petrol Fires in Closed Rooms
Petrol Fires in Closed Rooms D. F. NELSON
Dept. of Scientific and Industrial Research, Auckland, New Zealand Two petrol jires in closed rooms are reported. The fires were ra#id, intense, short-lived and self-extinguishing. The reconstruction of the first i s based on the scene examination later conjirmed by admissions of the alleged perpetrator. The second jire which was prepared during a training course for Police arson investigators (Auckland, July, 1968) was a n attempt to duplicate the main features of the first. Introduction Police and other experts arrived at the scene of the homicide described below 2 to 3 hours after it had taken place. When a Fire Brigade Officer inspected the scene, he suggested that a flash fire had lasted for a few seconds and had then extinguished itself due to lack of oxygen. By a fortunate coincidence this suggestion could be studied during a course for arson investigators that had been planned for the following week. Part of the course was the setting of a variety of fires in an old house which was about to be demolished because of motorway construction. Fire at Camp Bunn This homicide followed by a fire on 24th July, 1968, took place in an office on the mezzanine floor of a warehouse in a former military storage depot. . The office was 16 feet 6 inches by 12 feet with stud height 8 feet. I d the North wall was a group of three top-hinged casement windows each 18 inches wide and 24 inches high. The middle one was opened about 6 inches ; the others were closed. The window ledge was one foot wide and was used as a shelf. Furnishings were as illustrated in Figure 1. The shelves on the East wall were draped with curtains. '
Fig. 1. Plan of office at Camp Bunn (for details see text) 3
The victim's body was found lying between the desk and the window. The post-mortem examination showed that he had been shot several times and was dead before the fire. When the crime was discovered, the office and the victim's clothes had a strong petroleum smell. His hair was mostly burned off and his skin was blistered-bcth on exposed areas such as his face and also under his clothing. His jersey was mildly scorched consistent with its acting as a wick. The floor beneath the body and under scattered books had a damp, greasy appearance. The surface of the desk and objects on the desk such as a glass tray and the underside of a satchel also had greasy smears on them. The liquid used seemed to be a very volatile petroleum product such as motor spirit. This was confirmed by distilling visible quantities of inflammable liquid from a cushion on the floor and from the victim's clothing. Over a millilitre of liquid was distilled from the victim's singlet which had been obtained a t the postmortem examination about 6 hours after the fire. I t was identified by gas chromatography as the residues of motor spirit. Although the lighter fractions were still present, the relative proportion of heavy ends to light fractions had been increased in the order of 100 times. An explosion was indicated by (a) the position of a telephone directory weighing 4 pounds, and a private boxes directory weighing 11 ounces, and by a cup and saucer, which presumably had been on the ledge of the partly-opened window but were found outside the building below the window and (b) splashes of debris which were adhering to the wall across the corridor and t o the door of the adjoining office a t the end of the corridor. Diagonal smears on the corridor floor indicated that the door was probably a few inches ajar when the explosion took place. These splashes and smears were consistent with paint on the door and door frame being softened and blistered by the heat of an initial fire a t the doorway and then being blown across the corridor by the explosion. I t appeared that the explosion slammed the door shut, as found, but was not strong enough to blow out the windows (note that one window was partly open). There was superficial charring or scorching around the entire room, somewhat greater over the body and the desk but there was no apparent site of intense burning. The outer folds of the curtains in front of the shelves were charred more than the inner folds. I t was noted also that the window sides of the folds were more scorched than the door sides of the folds. The heat was sufficiently intense to crack the window panes and the glazing over a diploma, to blister paifit and to char the curtains. The fire was observed as an orange glow by the driver of a passing train but died down too rapidly for him to point it out t o his fireman. The offender appeared t o have been aware of the risk of a rapid fire or an explosion because the fire had been started in the corridor with a flame on the end of a stick 3 feet 9 inches long which was found in the corridor. He later admitted that after the shooting he had poured about a gallon of motor spirit over the body and the desk top and then led a trail through the door into the corridor. Sponge rubber nailed to the end of the above-mentioned stick was moLtened with petrol and lighted. This flaming torch was then thrown along the-corridor to ignite the petrol outside the office door. Fire at Wellington Street .This-fire was set on 31st July, 1968, during a course for Police arson investigators in an attempt to duplicate the fire a t Camp Bunn. The building was an old (70 years?) wooden house of the villa type in which there was a central passage with rooms opening from each side. The room used for the experiment was a t the front of the house. In the South wall, which was the front of the house, was a three-light, double-hung window with fixed side lights approximately 1 foot 6 inches, 3 feet and 1 foot 6 inches wide and 6 feet high. In the middle of the North wall, an interior partition of the 4
house, was an open fireplace. The room was approximately 12 feet by 12 feet with stud height 11 feet. The room was bare except for a sofa, wooden couch and a narrow mattress lying on the floor, as shown in Figure 2. The curtains hanging a t each end of the group of windows were of medium weight. A gallon of motor spirit was poured over the mattress, couch and floor, particularly towards the west side of the room, and a generous trail of motor spirit led through the door to a pool in the passage. The door was opened about 8 inches and the windows were closed. The pool of motor spirit in the passage was ignited by throwing a flaming torch through the front door of the house. This resulted in a vigorous swirling fire in the passageway-a whirlwind of fire which seemed reluctant to spread. This caused paint damage a t the doorway similar to that observed a t the earlier fire.
Fig. 2.
Plan of room a t Wellington Street (for details see text)
At 50 seconds from the ignition of the motor spirit in the passage, a flash-over occurred, as the flame spread into and involved the whole room which was rapidly filled with orange flame, accompanied by a roaring noise resembling a giant blowlamp. This roaring appeared to be due to the draught up the chimney as a belching tongue of orange flame and black smoke was seen to rise about 20 feet from the chimney. The fire lasted for 5-10 seconds then gradually died away. When the door which had been slammed shut by the blast was opened by the Fire Brigade 70 seconds after ignition, the room was filled with dense black smoke. The only fire observed was some flickering flames on the curtains, now down on the floor under the windows. Four of the window panes were cracked by the heat but none was blown out. The paintwork on the passage side of the door was severely blistered for about 2 feet up from the floor. Inside the room, all paintwork was seared and blistered, particularly on the East wall, but scorching on the wallpaper and scrim was largely obscured by sooting from an earlier experiment with a smouldering fire.
Conclusion I t is a question of semantics as to whether these two petrol fires should be described as low order explosions or intense conflagrations. The slamming of the door in each case indicates an appreciable blast. Notable features in these fires were the petrol trails outside the doors for starting the fires, the associated blistered paintwork a t low levels, the swirling action of the initiating fire a t Wellington Street and the long delay before the flash-over. Damage to the paintwork a t Camp Bunn similar to that a t Wellington Street indicates a similar initial swirling fire. The complete combustion of one gallon of petrol would require 11 kg of oxygen (calculating petrol as octane) and the total oxygen in either room would be about 13 kg. As flames would be extinguished before half the oxygen was consumed (Haldane and Graham-acetylene flame extinguished a t 13 per cent. oxygen in air) i t is clear that there was insufficient oxygen in the rooms to maintain a vigorous fire. The rapid burning of the petrol would consume oxygen a t a much greater rate than it could be replenished by access under closed doors or through windows (even partly opened) and the fires were thus self-extinguishing, leaving unburned petrol residues. Acknowledgments Thanks are due to the Auckland Metropolitan Fire Brigade, particularly Fire Prevention Officers H. Henderson and S. Thomas, and to the New Zealand Police, particularly Detective Inspectors J. Stevenson and P. Gentry, and Detective Senior Sergeant W. H. Shanks for their help in collecting and checking these data and for their advice and criticism of its presentation. Reference HALDANE, J . S., and GRAHAM, J. IVON,1935, Methods of Air Analysis, Griffin, London, p. 153.
Dept. of Scientific and Industrial Research, Auckland, New Zealand Two petrol jires in closed rooms are reported. The fires were ra#id, intense, short-lived and self-extinguishing. The reconstruction of the first i s based on the scene examination later conjirmed by admissions of the alleged perpetrator. The second jire which was prepared during a training course for Police arson investigators (Auckland, July, 1968) was a n attempt to duplicate the main features of the first. Introduction Police and other experts arrived at the scene of the homicide described below 2 to 3 hours after it had taken place. When a Fire Brigade Officer inspected the scene, he suggested that a flash fire had lasted for a few seconds and had then extinguished itself due to lack of oxygen. By a fortunate coincidence this suggestion could be studied during a course for arson investigators that had been planned for the following week. Part of the course was the setting of a variety of fires in an old house which was about to be demolished because of motorway construction. Fire at Camp Bunn This homicide followed by a fire on 24th July, 1968, took place in an office on the mezzanine floor of a warehouse in a former military storage depot. . The office was 16 feet 6 inches by 12 feet with stud height 8 feet. I d the North wall was a group of three top-hinged casement windows each 18 inches wide and 24 inches high. The middle one was opened about 6 inches ; the others were closed. The window ledge was one foot wide and was used as a shelf. Furnishings were as illustrated in Figure 1. The shelves on the East wall were draped with curtains. '
Fig. 1. Plan of office at Camp Bunn (for details see text) 3
The victim's body was found lying between the desk and the window. The post-mortem examination showed that he had been shot several times and was dead before the fire. When the crime was discovered, the office and the victim's clothes had a strong petroleum smell. His hair was mostly burned off and his skin was blistered-bcth on exposed areas such as his face and also under his clothing. His jersey was mildly scorched consistent with its acting as a wick. The floor beneath the body and under scattered books had a damp, greasy appearance. The surface of the desk and objects on the desk such as a glass tray and the underside of a satchel also had greasy smears on them. The liquid used seemed to be a very volatile petroleum product such as motor spirit. This was confirmed by distilling visible quantities of inflammable liquid from a cushion on the floor and from the victim's clothing. Over a millilitre of liquid was distilled from the victim's singlet which had been obtained a t the postmortem examination about 6 hours after the fire. I t was identified by gas chromatography as the residues of motor spirit. Although the lighter fractions were still present, the relative proportion of heavy ends to light fractions had been increased in the order of 100 times. An explosion was indicated by (a) the position of a telephone directory weighing 4 pounds, and a private boxes directory weighing 11 ounces, and by a cup and saucer, which presumably had been on the ledge of the partly-opened window but were found outside the building below the window and (b) splashes of debris which were adhering to the wall across the corridor and t o the door of the adjoining office a t the end of the corridor. Diagonal smears on the corridor floor indicated that the door was probably a few inches ajar when the explosion took place. These splashes and smears were consistent with paint on the door and door frame being softened and blistered by the heat of an initial fire a t the doorway and then being blown across the corridor by the explosion. I t appeared that the explosion slammed the door shut, as found, but was not strong enough to blow out the windows (note that one window was partly open). There was superficial charring or scorching around the entire room, somewhat greater over the body and the desk but there was no apparent site of intense burning. The outer folds of the curtains in front of the shelves were charred more than the inner folds. I t was noted also that the window sides of the folds were more scorched than the door sides of the folds. The heat was sufficiently intense to crack the window panes and the glazing over a diploma, to blister paifit and to char the curtains. The fire was observed as an orange glow by the driver of a passing train but died down too rapidly for him to point it out t o his fireman. The offender appeared t o have been aware of the risk of a rapid fire or an explosion because the fire had been started in the corridor with a flame on the end of a stick 3 feet 9 inches long which was found in the corridor. He later admitted that after the shooting he had poured about a gallon of motor spirit over the body and the desk top and then led a trail through the door into the corridor. Sponge rubber nailed to the end of the above-mentioned stick was moLtened with petrol and lighted. This flaming torch was then thrown along the-corridor to ignite the petrol outside the office door. Fire at Wellington Street .This-fire was set on 31st July, 1968, during a course for Police arson investigators in an attempt to duplicate the fire a t Camp Bunn. The building was an old (70 years?) wooden house of the villa type in which there was a central passage with rooms opening from each side. The room used for the experiment was a t the front of the house. In the South wall, which was the front of the house, was a three-light, double-hung window with fixed side lights approximately 1 foot 6 inches, 3 feet and 1 foot 6 inches wide and 6 feet high. In the middle of the North wall, an interior partition of the 4
house, was an open fireplace. The room was approximately 12 feet by 12 feet with stud height 11 feet. The room was bare except for a sofa, wooden couch and a narrow mattress lying on the floor, as shown in Figure 2. The curtains hanging a t each end of the group of windows were of medium weight. A gallon of motor spirit was poured over the mattress, couch and floor, particularly towards the west side of the room, and a generous trail of motor spirit led through the door to a pool in the passage. The door was opened about 8 inches and the windows were closed. The pool of motor spirit in the passage was ignited by throwing a flaming torch through the front door of the house. This resulted in a vigorous swirling fire in the passageway-a whirlwind of fire which seemed reluctant to spread. This caused paint damage a t the doorway similar to that observed a t the earlier fire.
Fig. 2.
Plan of room a t Wellington Street (for details see text)
At 50 seconds from the ignition of the motor spirit in the passage, a flash-over occurred, as the flame spread into and involved the whole room which was rapidly filled with orange flame, accompanied by a roaring noise resembling a giant blowlamp. This roaring appeared to be due to the draught up the chimney as a belching tongue of orange flame and black smoke was seen to rise about 20 feet from the chimney. The fire lasted for 5-10 seconds then gradually died away. When the door which had been slammed shut by the blast was opened by the Fire Brigade 70 seconds after ignition, the room was filled with dense black smoke. The only fire observed was some flickering flames on the curtains, now down on the floor under the windows. Four of the window panes were cracked by the heat but none was blown out. The paintwork on the passage side of the door was severely blistered for about 2 feet up from the floor. Inside the room, all paintwork was seared and blistered, particularly on the East wall, but scorching on the wallpaper and scrim was largely obscured by sooting from an earlier experiment with a smouldering fire.
Conclusion I t is a question of semantics as to whether these two petrol fires should be described as low order explosions or intense conflagrations. The slamming of the door in each case indicates an appreciable blast. Notable features in these fires were the petrol trails outside the doors for starting the fires, the associated blistered paintwork a t low levels, the swirling action of the initiating fire a t Wellington Street and the long delay before the flash-over. Damage to the paintwork a t Camp Bunn similar to that a t Wellington Street indicates a similar initial swirling fire. The complete combustion of one gallon of petrol would require 11 kg of oxygen (calculating petrol as octane) and the total oxygen in either room would be about 13 kg. As flames would be extinguished before half the oxygen was consumed (Haldane and Graham-acetylene flame extinguished a t 13 per cent. oxygen in air) i t is clear that there was insufficient oxygen in the rooms to maintain a vigorous fire. The rapid burning of the petrol would consume oxygen a t a much greater rate than it could be replenished by access under closed doors or through windows (even partly opened) and the fires were thus self-extinguishing, leaving unburned petrol residues. Acknowledgments Thanks are due to the Auckland Metropolitan Fire Brigade, particularly Fire Prevention Officers H. Henderson and S. Thomas, and to the New Zealand Police, particularly Detective Inspectors J. Stevenson and P. Gentry, and Detective Senior Sergeant W. H. Shanks for their help in collecting and checking these data and for their advice and criticism of its presentation. Reference HALDANE, J . S., and GRAHAM, J. IVON,1935, Methods of Air Analysis, Griffin, London, p. 153.