An employee was replacing a furnace in a customer's home and was installing a PVC exhaust pipe. The PVC pipe was to run directly over the water heater out the side of the home. He set his PVC cleaner and glue on top of the water heater (chest height) as he put the exhaust together. While installing the final piece, he cleaned the connection with the PVC cleaner and put the dabber back into the can. When he reached for the glue, he bumped the can of cleaner and it spilled on his chest. He caught the can with his hand but the contents spilled on the floor. The water heater ignited vapors from the cleaner and a fire started, causing first and second degree burns to his chest, right lower arm, right neck, earlobe, left armpit, and both lips.