Hot water wash #1 was locked out by cross cleaning solution EE, #2 hot wash unit was being utilized by Benchmark EE's to wash equipment. Benchmark EE's took a 15 min break. When they returned, one of the Benchmark EE's turned on switch for unit #2, a propane gas ignition occurred blowing the four 3""x4' doors off the cabinet of #2 and displacing bent stack.