The primary application of hot tar in the roofing industry is in commercial, low slope Built-Up Roofing (BUR) systems. In a BUR system, roofers use cotton or fiberglass mops to apply a base coat of hot liquid tar. Overlapping layers of asphalt-impregnated felt (tar paper) are then rolled over the hot tar. Then more tar is applied to form a leak-proof roofing system. The tar typically comes from the manufacturer in solid 100 pound cartons or kegs. It is either heated and transported in tanker trucks to the job site in liquefied form, or it is chopped into manageable pieces and fed into heating kettles for melting and use at the job site. The hot tar is then pumped to a hot lugger, which is a holding tank on the roof. From there, it is transferred to buckets or mop carts by the roofers for mopping onto the roof. Job Site Hazards 1. Contact with hot tar can result in serious burn injuries. The kettle operator is at risk of being splashed while feeding chunks or whole kegs into the kettle. 2. Slipping or tripping hazards can cause workers to stumble or fall. If the workers are carrying buckets of hot tar, they can be splashed with the hot tar. Freshly applied hot tar is very slick then becomes sticky as it cools. Both conditions are hazardous. 3. Carrying buckets of hot tar up or down ladders is very dangerous and potentially exposes the worker and those below to tar burns, in addition to the fall hazards of unsafe ladder use. 4. Ignition sources anywhere near the kettle or hot-lugger may result in fire because the vapors created by the high temperatures in these pieces of equipment are flammable. The flash point (the point at which a material will burn with an ignition source) of asphalt is 560 degrees F. To avoid fire or explosion the kettle temperature should always be maintained at least 25 degrees F below the flash point.
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