Abstract: Two laborers/painters were abrasive blasting boiler tubes at the Equistar Chemicals Plant. The employees were working in the "B" Boiler 48001 in unit OP-II Utilities Area. They were wearing protective equipment which included a supplied air respirator attached to a 12 pack of compressed air cylinders. A second subcontractor, Greenwade Services, Inc., was their confined space attendant. Work proceeded normally until some time after lunch, 12 a.m. At approximately 3:00 a.m. the attendant tried repeatedly to get the entrants to respond to the air horn. The attendant became concerned and called management to report the failure to communicate with the entrants. An AIS Basic employee was sent into the boiler to asses the situation. He found the two employees lying on opposite ends of the scaffolding. Equistar's HSE department later tested the compressed air 12 pack and found that it contained less than 5 percent oxygen.