Abstract: At 3:15 p.m. on July 12, 2018, an employee was performing abrasive blasting with metal shot in a tank that measured approximately 28-29 feet long by 8-9 feet high. The employee was wearing an Apollo supplied air respirator helmet (model number: 600) and exhaust ventilation was being used in the space. For an unknown reason, the employee collapsed and stopped breathing. The employee was found by a manager that began to perform CPR. However, the employee could not be revived and was determined dead. The incident investigation reported that the medical examiner was unable to determine a cause of death or manner of death. Carbon monoxide poisoning, as well as any preexisting medical conditions were ruled out. However, it was discovered that he had not had a respiratory medical evaluation prior to wearing the helmet, nor had he received training.