Aerosol Explosion Investigation
One evening a man purchased a couple aerosol spray cans of rubber and vinyl treatment for his automobiles. He worked nights and kept the aerosols in his 1981 El Camino through the night. He testified that the container in question was left on the passenger side floorboard in the front (there is no back seat in the El Camino).
The next day in the late afternoon the man returned to his El Camino to remove the aerosol. He said the aerosol was warm to the touch, but not hot. He used a towel to remove it and just as he did he dropped it and upon hitting the ground it exploded. The bottom exploded off and the body became a rocket, hitting him in the head. He was unconscious for a short time and paramedics came to take him to a nearby hospital for treatment.
The police took possession of the aerosol container and unfortunately disposed of it after keeping it for only a short while. The police had taken an evidence photo, but the container itself was gone. The sister can, purchased at the same time, remained. Since the incident took place in a state that follows Federal (Daubert) Rules of Evidence, the lack of the actual evidence was a serious challenge.
Nevertheless, by following the principles of failure analysis, certain conclusions could be reached. A 1981 El Camino was purchased for testing in Tucson, Arizona. Under weather conditions considerably more severe (hotter) than the weather on the day and location of the incident, the maximum temperature of an identical aerosol can on the floorboard of the El Camino was determined to be 120.2F. The aerosol comes packaged in a DOT 2Q container.
In separate experiments, the pressure of the aerosol product was measured to be 150 psig at 130 F. This is well within DOT specifications for a DOT 2Q container, which is 180 psig at 130 F. However, the El Camino simulations showed that the temperature of the aerosol product was below 130 F on the day of the explosion, which in turn means that the pressure inside the aerosol container was less than 150 psig at the time of the explosion. The Department of Transportation requires that the burst pressure of a DOT 2Q container be greater than 270 psig.
The fact that it exploded at a pressure below 150 psig was one piece of evidence of a defect in the container bottom.
In hydro pressure tests on an identical exemplar aerosol product, the top began to deform at 175 psig, was fully expanded at 200 psig, and developed a leak at the "top" double seam at 340 psig. The bottom never everted nor leaked nor failed in any manner. This result supports the view of aerosol industry personnel that tops will expand and fail before bottoms. One can conclude from the top-before-bottom rule that there is something defective with the bottom when it deforms and explodes away before the top.
In a heat-to-burst test, the top (not the bottom) of the aerosol product exploded off at 176 F to 190 F. One thermocouple is attached to the can bottom (176F) and another to the can side wall (190F). Note that 176 F to 190 F are well outside of the temperature range possible in a 1981 El Camino under anything even close to the incident weather conditions. Clearly, overheating alone did not cause the explosion.
The fact that the top exploded off in the heat-to-burst test, and not the bottom, was also significant. Research published in peer-reviewed scientific literature by aerosol industry personnel indicates that aerosol tops will deform and explode off non-defective containers before bottoms. In fact, in hydro pressure tests reported in the scientific literature by the aerosol industry, the tops need to be constrained in order to test the deformation and burst pressures of bottoms. Therefore, if the aerosol industry publication is true, anytime a bottom deforms and explodes off before the top, that is an indication that there is something unusual with the bottom. Since it was the bottom that exploded from the incident container, this was evidence of a defect within the bottom of that container (which had been thrown away by the police).
It was concluded that the aerosol product that exploded must have been manufactured in such a way that it could not withstand accidental dropping. No one denied that the accidental dropping played a role. However, such accidental dropping is highly foreseeable and aerosol products should be designed and manufactured in such a way to withstand such reasonable and foreseeable impact.
The case settled prior to trial, in spite of the fact that the state followed Federal Rules of Evidence and that the actual evidence had been thrown away by the police.
Dr. Michael Fox of Chemaxx, is accredited in Aerosol Technology by the Center for Professional Advancement as well as the British Aerosol Manufacturers Association, and certified by the DOT in the transportation of hazardous materials. (the DOT regulates aerosol containers and the products that can go in them). Dr. Fox is a Certified Fire & Explosion Investigator who is also an aerosol expert. He made presentations at national societies on the fire and explosion hazards associated with aerosols and was the first to publish a peer-reviewed paper on aerosol failures. He now leads the field in the number of peer-reviewed papers on aerosol failures.
©2006 CHEMAXX, INC