Abstract: At approximately 8:53 a.m. on March 18, 2008, Employee #1 and #2 were working on the production line of a manufacturing process. The facility manufactured aerosol cans that were partially filled with various chemical products. The cans were pressurized with propellants that included carbon dioxide, Freon-134A, and two highly flammable propellants, A-70 (propane and isobutane), and A-31 (isobutane), which both were maintained on the facility and in quantities that were in excess of 10,000 pounds, thus covered by the Process Safety Management standard. The propellants were injected into the cans via infeed lines from the propellant tanks located on an adjacent tank farm. Following the injection of the propellant, a conveyor system moved the cans through two openings in a common wall of a gashouse. Employees needed to begin a new aerosol product run, which required switching over the propellants from Freon-134A to A-70. Employee #1 and a coworker purged the A-70 return propellant line inside the gashouse for an extended period (at least 20 minutes) due to a vapor lock. This extended purging process was a somewhat common practice when significant changes in ambient temperatures occurred during the winter months. Because of the extended purging, the A-70 propellant leaked into the production area from the gashouse via the two conveyor openings. An electrical forklift of a Class 1 Division I and E rating, which was not suitable for such a flammable environment, was in the building at the time of the gas leak. Employee #1 attempted to relocate the forklift when the A-70 propellant gas leak within the building ignited and caused the building to explode. Employee #1 and #2 suffered critical injuries from the explosion. Employee #1 sustained third degree burns, whereas Employee #2 sustained third degree burns and unspecified broken bones after being trapped underneath the collapsed structure. Both employees were originally transported to a local hospital for initial treatment. Upon receiving this treatment, they were reassessed and transferred to the burn centers of different medical centers in different locations where they underwent medical care and were hospitalized. The investigation revealed that the gashouse contained a ventilation system, which was not operational and had blocked intake exhaust ventilation vents, and an alarm system that had been turned off, which was connected to an LEL sensor in the gashouse, either of which would have likely prevented the explosion.