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Watch a gas can explode in a lab test

The plastic gas cans used by millions of Americans carry a risk of explosion under certain limited conditions, according to the results of separate laboratory scientific tests commissioned by a plaintiff’s attorney, the ATF and the gas can industry.

“'Is there a problem?' was the question,” said Ali Rangwala, director of the combustion lab at Worcester Polytechnic Institute in Massachusetts, whose team conducted the industry’s test. “And our answer to that was, ‘Yes, this is a problem.’… We definitely know that the problem exists, and we know that it's not a good idea, for example, to keep the can close to empty in your garages.”

With the support of the industry, Rangwala and his team at WPI conducted tests in 2010 under contract to a technical standards organization that issues standards for plastic gas cans. WPI published a scientific paper this past spring, and it showed that results were the same for all the gas can brands WPI tested. 

 “Criteria for flame propagation to the inside of a portable gasoline container have been determined for fuel storage and pouring scenarios,” the paper stated. “Extremely small gasoline volumes and/or low ambient temperatures produce conditions inside the PGC [portable gasoline container] that may allow flame propagation to occur.”

The WPI scientists found that these conditions present the highest risks for explosions inside the cans: a very small volume of gasoline inside the can – a few teaspoons; cool temperatures; and tilting the gas can at a 42 degree angle, a common angle for pouring.

Rangwala and graduate student Brian Elias both told NBC News that the industry group had asked them to test whether plastic gas cans presented an explosion hazard, and that their test results indicated the cans do pose a hazard, under these limited conditions. NBC News asked Rangwala and Elias to replicate the tests it had conducted for the industry group, under the same conditions, with NBC News cameras present.

The WPI scientists tested five separate 5-gallon gas cans filled with a tiny amount of gasoline – 30 milliliters. The gas vapor mixtures inside each of the cans ignited when an open flame was held under the open spout of the can, which was positioned at a pouring angle. Each time, a fireball burst through a sheet of aluminum foil covering a square hole that Elias had cut in each can, so that the force of an ignition would “vent” from the can in a controlled direction. For safety reasons, WPI did not allow unvented uncontrolled ignitions. 

Asked what the tests showed, Rangwala said, “It basically tells us that there is an issue with the gas cans … and it needs to be addressed.”

The federal government’s Bureau of Alcohol, Tobacco, Firearms and Explosives conducted its own tests of plastic gas cans at its Fire Research Laboratory in Maryland in December 2010 as part of a criminal investigation involving a father whose six-year-old daughter had died of injuries sustained after he poured diesel fuel onto a burning fire pit and his daughter became engulfed in flames. 

ATF tested various mixtures of diesel and gasoline, as well as gasoline alone, and found that cans containing higher amounts of gasoline than WPI tested also experienced ignitions of gas vapor mixtures from inside the cans, when an open flame was held beneath the open spout. According to the ATF’s lab report on those tests, those combustions caused the cans to expulse “jets” of flame between 1 and 3.5 meters long – approximately 3 to 7.5 feet. In those tests, the cans’ sides appear to be supported by a harness and did not rupture

Scientists hired by plaintiff’s attorney Diane Breneman, who has represented more than 30 alleged victims of gas can incidents, found that “explosions of gasoline stored in commercially available PPGCs [portable plastic gas cans] can and do occur under foreseeable conditions when their [gas vapor mixture] concentration is within the flammable range.” The tests, by Berkeley Engineering and Research in California, showed that 22 of 58 trials involving ignition of fuel from inside gas cans resulted in the explosions inside the cans.

Rangwala said that scientific proof of the existence of an explosion hazard should not lead to the conclusion that consumers stop using plastic gas cans. 

“If there is the right kind of education given to the consumer related to the situation,” Rangwala said, “the hazard can be avoided.” Just as consumers avoid hazards while driving cars, or using kitchen stoves.

William Moschella, an attorney for the Portable Fuel Container Manufacturers Association, a trade group of plastic gas can manufacturers, says that today gas cans “are very safe.” He told NBC News that most alleged incidents of internal can explosion have involved consumer misuse – such as pouring gasoline on a fire. He argued that all the incidents more likely have resulted from vapor explosions occurring outside the cans, and asserted that no one has proven in court that an explosion incident resulted from an ignition inside a can.

“This is really only occurring in a laboratory environment,” Moschella said. “We haven't seen a case where that has been demonstrated.” He also said that the ATF tests “did not demonstrate internal combustion in a can,” and that laboratory tests do not represent “a real life situation that we’ve ever seen.”

“It’s not clear at all that what is occurring in the real world, in real life, is that gas cans are exploding.”

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