This month we saw CAL-OSHA issue citations to a roofing company after two of its employees were literally blown off an asphalt tanker and ten (10) feet to the ground. Both workers sustained serious burns to large portions of their bodies. But after hearing all the comments about “safety is just common sense” I wonder how many professionals, including safety professionals, actually know that an asphalt tanker and kettles can and most often do contain a flammable atmopshere? One fact we do know, at least two workers and their supervisor were NOT aware of this hazard, as the two employees standing on top of a tanker truck were attempting to turn the truck’s discharge pipe to face another direction and their supervisor instructed them to heat the pipe with a propane torch in order to loosen it. The tanker was half-filled with hot liquid asphalt meaning there was plenty of vapor space in the tanker, coupled with the fact that heated liquid asphalt releases flammable vapors made for the perfect storm.
Roofing asphalt is one of those hazardous materials that is shipped as a Class 9 HAZMAT, meaning there is no indication that the HAZMAT is flammable, as shown above. The NFPA Diamond also does NOT indicate that the material is flammable; but heated asphalt will generate vapors and inside a container it can achieve its LEL. However, if we were to look up “asphalt” in our 2016 DOT Guidebook we see the following:
HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. Vapors may form explosive mixtures with air. Vapors may travel to source of ignition and flash back. Most vapors are heavier than air. They will spread along ground and collect in low or confined areas (sewers, basements, tanks). Vapor explosion hazard indoors, outdoors or in sewers. Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. Runoff to sewer may create fire or explosion hazard. Containers may explode when heated. Many liquids are lighter than water. (ERG, 2016)
Cal/OSHA issued three workplace safety citations for this accident, with proposed penalties of $24,575. Two of the citations are serious, and one is regulatory in nature. One of the serious citations involves the failure to ensure the tanker truck was equipped with a 42-inch guardrail. This could have helped ensure the workers did not fall 10 feet as they did. The other serious citation was for allowing a source of ignition to be introduced where the flammable gases exceeded 25% of the lower explosive limit. Source
Here is an EXCELLENT article for more on the hazards of asphalt:
https://www.etnyre.com/%5Csafety%5CDanger%20Hot%20Asphalt.pdf