Abstract: At 9:07 a.m. on April 3, 2018, an employee was working for a firm that provided support activities for oil and gas operations. The facility where he worked was a fixed site. It consisted of a commercial shop, an office building, and a yard. His employer repaired or fabricated tankers designed for propane, petroleum, food, vacuum storage, chemicals, and so forth. The injured employee was an employee of the employer; i.e., not from a temporary labor agency. The incident occurred at his place of employment. He did have a supervisor for the task he was performing. The employee was performing a routine activity, making repairs to a propane tanker. As he was using a welding machine around the manway of the propane tank. As he was welding a nut on a propane tank, an explosion occurred. The employee sustained second- and third-degree burns to his face, neck, chest, stomach, back, and his bilateral upper extremities (his arms and hands). He was medically treated in Arrowhead Regional Medical Center in Colton, CA. He was hospitalized. The employer's representative reported the injury to the San Bernardino District Office at 3:20 p.m. the next day. The employer did meet the Division's reporting requirements. A CSHO from San Bernardino District office arrived at the site and opened the investigation at 2:30 p.m. on April 19, 2018. It was found that prior to and during the course of investigation, including but not limited to, on April 3, 2018, the employer failed to ensure that the propane tank had been completely emptied, purged of flammable vapors, and tested, using an appropriate device, for flammable vapors prior to utilizing a welding machine to make repairs. As a result, on April 3, 2018 an employee sustained serious injury from an explosion that occurred while he made repairs with the use of welding machine around the manway of the propane tank. One of the factors that caused the accident was that employer failed to ensure that the propane tanker had been completely emptied, purged of flammable vapors, and tested, using an appropriate device, for flammable vapors prior to utilizing a welding machine to make repairs. If the propane tanker had been completely emptied, purged of flammable vapors, and tested prior to utilizing a welding machine it would have prevented the accident. A Serious Accident-Related violation of Title 8 CCR 5420(a)(2) was determined. The employer was cited.