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Michael Fox, PhD.



Aerosol Filling Plant Fire

Chemaxx was asked to investigate the cause of an explosion at an aerosol filling plant (AFP) that had manufactured aerosol products for over 16 years.

pickup truck used for pizza delivery rolled down the slope, crashed through the chain link fence gate and impacted the 18,000-gallon tank's piping
Aerial View of Aerosol Filling Plant Fire

One employee who worked in the aerosol filling room received horrific burns that included the loss of his ears and hands.

The plaintiff's theory was that the outside propellant storage tanks were in such bad condition that the propellant supplier should not have delivered to them and/or should have alerted the supplier to require an inspection of the inside of the AFP. However, at the time of the fire there were no leaks at the tanks and no deliveries in progress. There was no fire at the tanks during the entire event. The fire originated inside the plant, not at the tanks.

aerial photo of explosion
Burn Injuries.

The equipment at the AFP was a hand-operated, semiautomatic, 1984 aerosol filling machine. Annual revenues of the AFP were $4-6 million with a net profit of 10% or $400,000 to $600,000 profit.

The fact that aerosols have "contents under pressure" and "flammability" can present risks of explosion and fire under some circumstances, such as when they are not properly manufactured. Therefore, the manufacture of aerosols is regulated by the United States Department of Transportation (DOT). Among other things, the DOT regulates the different types of aerosol containers and the pressures of the contents and propellants that are allowed to go into each type of container. As a final safety check the DOT requires that each and every aerosol pass through a hot water bath to test each aerosol for leaks and mechanical integrity before it is passed along to any consumer. Manufacturing aerosols without a waterbath is a violation of Federal Code.

The propellant used was A-70. The "A" stands for "Aerosol" and the "70" means that this propellant will have a vapor pressure of 70 psig at a temperature of 70° F. For example, A-46 is an aerosol propellant that has a pressure of 46 psig at 70° F. Another important property of aerosol propellants is their vapor pressure at 130° F. A-70 has a vapor pressure of almost 180 psig at 130° F.

The National Fire Protection Association (NFPA) develops consensus standards on matters affecting fire safety. Very often state or local governments will adopt various NFPA standards into law. The NFPA Standards themselves are not "law," but once adopted by the State or Local Government, they become "law."

In 1990 the NFPA developed a Code for the Manufature and Storage of Aeosol Products referred to as NFPA 30B. The second edition was published in 1994 and the third edition in 1998. The purpose of NFPA 30B is to provide minimum requirements for the prevention and control of fires and explosions in facilities that manufacture, store or display aerosol products. The AFP fell into that category.

In 1997, and perhaps earlier, the State adopted the International Fire Code which in turn includes NFPA 30B and NFPA 58. Therefore, the requirements of NFPA 30B and NFPA 58 were "law" in the State of the AFP well before the events at the AFP in 2004.

It must be emphasized that the State's Fire Prevention Code encompasses both NFPA 30B and NFPA 58. The focus of NFPA 30B is the Aerosol Filling Room while the subject of NFPA 58 includes the outside tanks. The local Fire Department had responsibility and authority for both the inside and the outside of the AFP.

NFPA 30B requires many things. However, there are five larger elements of NFPA 30B that are worth mentioning:

  • The first is the requirement for a Gas House which is 25 ft. from propellant tanks and from any flammable and combustible liquids. The Gas House is where the aerosols are filled with product and propellant. It may be separate building or within an existing structure, but if inside it must be separated from inside areas by noncommunicating walls. The idea behind the Gas House is that it is a controlled environment in which it is easier to eliminate the chances of anything going wrong, such as a fire or explosion. For example, the chances of a forklift driving by that could ignite a fire or explosion is zero.
  • The second requirement is for continuous nonrecirculating ventillation, ½ ft. above the floor. There is also the requirement for emergency (increased) floor-level ventillation that is activated automatically by a gas detection system.
  • The third requirement is for a gas detection system with audible or visible alarms that activate when the gas vapors hit 20% of the lower explosive limit (LEL). In other words, this first-level alarm tells the operator that something is wrong when there is still a 4X safety factor and there is still an opportunity to fix the problem safely without shutting down. The gas detectors are also interlocked to activate emergency (increased over normal) ventillation at 20% LEL. In addition, the alarms are interlocked to automatically shutdown propellant supply at 40% LEL, which is a 2.5X safety factor. Safety measures such as these eliminate the chances of fires and explosions.
  • A fourth requirement covers Powered Industrial Trucks or Forklifts. All forklifts are to comply with NFPA 505, which in turn would require explosion-proof forklifts in a plant such as the AFP. The forklift that was the most likely ignition source for the AFP explosion was not explosion-proof.
  • A fifth requirement is that all electrical equipment be suitable for Class I, Division I locations. In other words, explosion-proof.

The investigation revealed that, among other things:

The AFP did not have an NFPA 30B Gas House,
The AFP did not have any ventillation,
The AFP did not have any gas monitors or alarms,
The AFP did not use explosion-proof forklifts, and
The AFP did not have a hot water tank.

According to the testimony of more than one employee, there was little to no safety training at the AFP. One worker testified that when workers would bring safety issues to the attention of their supervisor, he would say:

"Just quit being a pussy and do your work."

One worker testified to showing plant management and the plant chemist the need for a Gas House per the Aerosol Handbook as well as the need for ventilation. He testified that he had multiple conversations with management and that he also made a request for a hand held gas alarm, but:

"It just got blowed off."

Chemaxx determined that the most likely ignition source for the fire and explosion was a non-explosion-proof forklift that had just passed by an open door to the Aerosol Room.

Given the position of the forklift at the time the fire was first ignited, Chemaxx determined that the most likely source of fuel for the initial fire was a combination of leakage from finished aerosol products outside the Aerosol Room plus a known earlier leak that day in a pipe within the Aerosol Room. Had it not been for the leaking finished aerosol products it is possible that nothing would have ignited as the concentration of flammable vapors at the forklift would have been below the Lower Explosive Limit (LEL) as the forklift passed by. The explosion did not initiate until the forklift had passed by the open door to the Aerosol Room and was adjacent to a rack of finished aerosol products.

The underlying non-physical causes for the fire and explosion were human error, incompetence and/or negligence on a massive scale.

The evidence left no choice but to conclude that the AFP had made conscious decisions, more than once, to put money ahead of the safety of their employees. With an annual revenue that was $4-6 million and their profits on the order of $400,000-$600,000 per year the AFP could have eliminated this fire and explosion in the Aerosol Room for just a few thousand dollars by installing floor level ventilation and flammable gas monitors.

The State's LP Gas Bureau also inspected the plant's A-70 storage tanks each and every year, approved them for propellant storage and never found anything that prompted them to inspect inside the plant. The tanks were from a converted double barrel bobtail and are pictured below. During the last inspection the state did recommend that the tanks be painted.

Storage Tanks

The Local Fire Department not only had the legal responsibility to inspect the AFP both inside and outside, but they also had the legal authority to make them comply. For reasons never fully understood, not only did they not make them comply … they didn't find anything wrong.

It was Chemaxx's opinion, based on all the evidence that the AFP willfully failed to protect the health and physical safety of their employees and that failure was the proximate cause of the fire and explosion and the plaintiff's injuries. It was Chemaxx's further opinion that the safeguards that are normally built into the system via the regular inspections by the Fire Department and State completely broke down. This breakdown of the Fire Department and State to responsibly and competently carry out their inspection duties and to exercise their authority was a strong contributing cause.

The case settled before trial.

Dr. Fox is a Certified Fire & Explosion Investigator with extensive experience in metallurgy, corrosion and failure analysis who is also accredited in aerosol technology.. He has 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 (8) on aerosol failures, fires and explosions. His aerosol-related paper in 2007 won the Paper-of-the-Year Award from the ASM Journal of Failure Analysis & Prevention. For further details on Dr. Fox's qualifications as an aerosol expert witness click here.