An operator was working to remove a pressure gauge on what was assumed to be depressurized tubing. The upstream piping the pressure gauge tubing was connected to had been isolated, de-pressured and air-gapped so that this section of line was positively and physically isolated from the process. However, during the work to isolate the process line the section of tubing leading to the pressure gauge had been left blocked in and butane was trapped between two valves in the tubing. When the operator broke the tubing fitting, he was splashed with the trapped butane, ultimately resulting in an OSHA recordable incident.
