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FIRES AND EXPLOSIONS WITH COMPRESSED GASES: Report of an Accident
Brit. J. Anaesth. (1965), 37, 140
FIRES AND EXPLOSIONS WITH COMPRESSED GASES Report of an Accident BY YUSUKE ITO, H . HORIKAWA AND K. ICHIYANAGI
Department of Anesthesiology, Niigata University School of Medicine, Niigata, Japan SUMMARY
A case of near-fire with resultant burns to an anaesthetist is reponed. This happened upon opening the regulator valve of an oxygen cylinder which probably had been contaminated with liquid paraffin. Possible mechanisms of the accident is discussed. Fires and explosions are hazards inherent in any occupation in which compressed gases are handled. Physicians, especially anaesthetists, are always being exposed to these dangers although it is agreed that most of these can be prevented by constant vigilance and patient observation of the accepted principles of prevention. A search of the literature disclosed only a few accidents of this type (Thomas, 1951, 1957). Many things, however, can escape the limits of human attention so easily that fires and explosions resulting from faulty handling of compressed gases must be more frequent than we think. It seems, therefore, worth reporting a case we have recently encountered in an attempt to call attention to possible retributions one might receive as the result of relaxed precautions.
The cylinder was tested for its content after its outlet was cleaned thoroughly. A reducing valve with a gauge indicated a pressure of about 100 arm. (1,500 p.s.i.). No flame was seen on opening the valves. Comparison with another oxygen cylinder using a paramagnetic oxygen analyzer showed the content to be pure oxygen. The gas itself did not burn on lighting but simply supported the combustion of matches.
ACCIDENT REPORT While a patient was being anaesthetized for cardiac catheterization a laboratory technician who had been helping the team was requested to bring a 500-litre oxygen cylinder from a nearby ward. The anaesthetist, in order to check if the cylinder contained enough oxygen, opened the cylinder valve and then the flowregulating valve of the regulator (fig. 1). At this moment, in the middle of the dimly lit room, a whitish-red flame, about 10 cm long, jetted out of the regulator outlet. The anaesthetist quickly closed the cylinder valve. Although it took only 3 to 5 seconds to terminate the gasflow, the regulator became untouchably hot. The anaesthetist later found a few second-degree burns, 6 X 6 mm, 3 x 3 mm and 8 x 4 mm, respectively, and first-degree burns on his palms and fingers. No other persons were injured nor was the catheterization interrupted by this accident. The anaesthetist recollected that the laboratory technician had been handling liquid paraffin for the measurement of blood-gases. On inquiry it was revealed that the technician carried the cylinder by seizing its neck with a paraffin-soiled hand.
FIG. 1
COMMENT
The material that burnt with a bright flame was probably liquid paraffin which had contaminated the regulator outlet. Dust on the cylinder outlet or in the regulator may have been responsible for the initial combustion in the regulator at the moment of opening the cylinder valve, though
141
FIRES AND EXPLOSIONS WITH COMPRESSED GASES this possibility is remote since the cylinder with that particular regulator already attached had been used a few times in the ward without event. In either case—paraffin or dust, or both—combustion might not have occurred if the anaesthetist would have opened the cylinder valve very much more slowly than he actually did. The admirable illustration by Macintosh, Mushin and Epstein (1958) points out that the sudden inrush of a gas at 100 atm. into the small ductspace of the regulator can raise, by its compression effect, the low pressure gas inside to a temperature as high as 800°C, or possibly 2,000°C or more, depending on the speed of the pressure build-up. It seems an easy matter for this astonishingly hot gas to ignite liquid paraffin, the lowest ignition point of which is about 150°C, even though a good part of the heat produced may be dissipated to the surrounding metal walls before the gas reaches the regulator outlet. In order to reduce the production of heat the volume of the regulator's duct-space should be as small as possible. The complex shape of the duct-space may also mitigate the sudden build-up of the high pressure. In this regard the straight and relatively large duct-space of the simple regulator used in the present case may have contributed to the occurrence of the accident. This regulator, used commonly for oxygen therapy in the ward, has no pressure-reducing mechanism incorporated. The high pressure of the cylinder is directly imposed on the flow-regulating valve. Therefore, it is not only difficult to regulate the flowrate but it is also dangerous. For reasons of economy we have not been successful in replacing them all with safer pressure-reducing valves.
It was fortunate that a priceless lesson was derived from this accident at the cost of only slight burns to one of us. Influenced by this experience, training in the handling of compressed gases has been fortified in the department and in the hospital. REFERENCES
Macintosh, R., Mushin, W. W., and Epstein, H. G. (1958). Physics for the Anaesthetist, 2nd ed, p. 385. Springfield: Thomas. Thomas, G. J. (1951). Do you know—fires and explosions. Newsletter, Amer. Soc. Anesth., 15, 10 (Apr.). (1957). Do you know—fires and explosions. Newsletter, Amer. Soc. Anesth., 21, 56 (Sept.). INCENDIES ET EXPLOSIONSJ AVEC LES GAZ COMPRIMES: RAPPORT D UN ACCIDENT SOMMAIRE
On rapporte le cas d'un d6but d'incendie ayant caus£ des bnllures a un anesthesiste. (Test arrive lors de l'ouverture de la soupapc rigulatrice d'une bouteille d'oxygene qui ayait 6t6 probablement souillee par de la paraffine liquide. On discute les mecanismes possibles de l'accident.
BRANDE UND EXPLOSIONEN MIT KOMPRIMIERTEN GASEN: BERICHT OBER EINEN UNFALL ZUSAMMENFASSUKG
Es wird iiber den Fall eines Nah-Brandes mit sich daraus ergebenden Verbrennungen bei einem Anasthesisten berichtet. Der Vorfall ereignete sich beim Offnen des Regulationsventils einer Sauerstofflasche, die wahrscheinlich mit fliissigem Paraffin verunreinigt worden war. Die moglichen Unfallmechanismen werden diskutiert.
FIRES AND EXPLOSIONS WITH COMPRESSED GASES Report of an Accident BY YUSUKE ITO, H . HORIKAWA AND K. ICHIYANAGI
Department of Anesthesiology, Niigata University School of Medicine, Niigata, Japan SUMMARY
A case of near-fire with resultant burns to an anaesthetist is reponed. This happened upon opening the regulator valve of an oxygen cylinder which probably had been contaminated with liquid paraffin. Possible mechanisms of the accident is discussed. Fires and explosions are hazards inherent in any occupation in which compressed gases are handled. Physicians, especially anaesthetists, are always being exposed to these dangers although it is agreed that most of these can be prevented by constant vigilance and patient observation of the accepted principles of prevention. A search of the literature disclosed only a few accidents of this type (Thomas, 1951, 1957). Many things, however, can escape the limits of human attention so easily that fires and explosions resulting from faulty handling of compressed gases must be more frequent than we think. It seems, therefore, worth reporting a case we have recently encountered in an attempt to call attention to possible retributions one might receive as the result of relaxed precautions.
The cylinder was tested for its content after its outlet was cleaned thoroughly. A reducing valve with a gauge indicated a pressure of about 100 arm. (1,500 p.s.i.). No flame was seen on opening the valves. Comparison with another oxygen cylinder using a paramagnetic oxygen analyzer showed the content to be pure oxygen. The gas itself did not burn on lighting but simply supported the combustion of matches.
ACCIDENT REPORT While a patient was being anaesthetized for cardiac catheterization a laboratory technician who had been helping the team was requested to bring a 500-litre oxygen cylinder from a nearby ward. The anaesthetist, in order to check if the cylinder contained enough oxygen, opened the cylinder valve and then the flowregulating valve of the regulator (fig. 1). At this moment, in the middle of the dimly lit room, a whitish-red flame, about 10 cm long, jetted out of the regulator outlet. The anaesthetist quickly closed the cylinder valve. Although it took only 3 to 5 seconds to terminate the gasflow, the regulator became untouchably hot. The anaesthetist later found a few second-degree burns, 6 X 6 mm, 3 x 3 mm and 8 x 4 mm, respectively, and first-degree burns on his palms and fingers. No other persons were injured nor was the catheterization interrupted by this accident. The anaesthetist recollected that the laboratory technician had been handling liquid paraffin for the measurement of blood-gases. On inquiry it was revealed that the technician carried the cylinder by seizing its neck with a paraffin-soiled hand.
FIG. 1
COMMENT
The material that burnt with a bright flame was probably liquid paraffin which had contaminated the regulator outlet. Dust on the cylinder outlet or in the regulator may have been responsible for the initial combustion in the regulator at the moment of opening the cylinder valve, though
141
FIRES AND EXPLOSIONS WITH COMPRESSED GASES this possibility is remote since the cylinder with that particular regulator already attached had been used a few times in the ward without event. In either case—paraffin or dust, or both—combustion might not have occurred if the anaesthetist would have opened the cylinder valve very much more slowly than he actually did. The admirable illustration by Macintosh, Mushin and Epstein (1958) points out that the sudden inrush of a gas at 100 atm. into the small ductspace of the regulator can raise, by its compression effect, the low pressure gas inside to a temperature as high as 800°C, or possibly 2,000°C or more, depending on the speed of the pressure build-up. It seems an easy matter for this astonishingly hot gas to ignite liquid paraffin, the lowest ignition point of which is about 150°C, even though a good part of the heat produced may be dissipated to the surrounding metal walls before the gas reaches the regulator outlet. In order to reduce the production of heat the volume of the regulator's duct-space should be as small as possible. The complex shape of the duct-space may also mitigate the sudden build-up of the high pressure. In this regard the straight and relatively large duct-space of the simple regulator used in the present case may have contributed to the occurrence of the accident. This regulator, used commonly for oxygen therapy in the ward, has no pressure-reducing mechanism incorporated. The high pressure of the cylinder is directly imposed on the flow-regulating valve. Therefore, it is not only difficult to regulate the flowrate but it is also dangerous. For reasons of economy we have not been successful in replacing them all with safer pressure-reducing valves.
It was fortunate that a priceless lesson was derived from this accident at the cost of only slight burns to one of us. Influenced by this experience, training in the handling of compressed gases has been fortified in the department and in the hospital. REFERENCES
Macintosh, R., Mushin, W. W., and Epstein, H. G. (1958). Physics for the Anaesthetist, 2nd ed, p. 385. Springfield: Thomas. Thomas, G. J. (1951). Do you know—fires and explosions. Newsletter, Amer. Soc. Anesth., 15, 10 (Apr.). (1957). Do you know—fires and explosions. Newsletter, Amer. Soc. Anesth., 21, 56 (Sept.). INCENDIES ET EXPLOSIONSJ AVEC LES GAZ COMPRIMES: RAPPORT D UN ACCIDENT SOMMAIRE
On rapporte le cas d'un d6but d'incendie ayant caus£ des bnllures a un anesthesiste. (Test arrive lors de l'ouverture de la soupapc rigulatrice d'une bouteille d'oxygene qui ayait 6t6 probablement souillee par de la paraffine liquide. On discute les mecanismes possibles de l'accident.
BRANDE UND EXPLOSIONEN MIT KOMPRIMIERTEN GASEN: BERICHT OBER EINEN UNFALL ZUSAMMENFASSUKG
Es wird iiber den Fall eines Nah-Brandes mit sich daraus ergebenden Verbrennungen bei einem Anasthesisten berichtet. Der Vorfall ereignete sich beim Offnen des Regulationsventils einer Sauerstofflasche, die wahrscheinlich mit fliissigem Paraffin verunreinigt worden war. Die moglichen Unfallmechanismen werden diskutiert.