Abstract: At 10:30 a.m. on September 12, 2019, two employees were working for a firm that provided electrical work and service. They were at a site, replacing a defective expansion valve on the site's number 5 water chiller. The chiller contained approximately 60 lbs. (27 kg.) of R-22 refrigerant, or Freon. The two workers had crawled under the chiller to place vacuum pump connections on the system, and they had pumped out the Freon from the chiller. They were taking off the R-22 Freon line to remove the expansion valve. They were heating a soldered nipple or joint on the line. One employee operated the torch, while the other helped him. Both employees were wearing T-shirts. The employee operating the torch was wearing a cotton T-shirt. The helper had pliers on the line to try to pull apart the line from the heated soldered joint. When the joint came apart, a mixture of residual Freon and oil in the line was released. A flash fire occurred, and the employee operating the torch received second-degree burns to his right arm, neck, cheek, and chest. He was hospitalized for two or more days. The safety data sheet for R-22 manufactured by Dupont notes that while R-22 is not flammable in air temperatures up to 212 degrees F (100 degrees C) at atmospheric pressure, mixtures of this substance with high concentrations of air at elevated pressure and/or temperature can become combustible. Further, the entire time the employees were working on the chiller, the 480-volt disconnect panel box on the other side of the chiller was not locked out. The employer has revised the procedure so that the line being serviced is purged with nitrogen.