The worker was welding a tank on Wednesday afternoon when the explosion happened at Jeff Crockett’s Custom Welding and Fabricating in Jefferson, Kanawha County Sheriff Mike Rutherford said.
He appeared to have been killed instantly, Rutherford said.
A woman was working in an office at the business but was not injured in the blast, officials said.
The state Fire Marshal’s Office, the Occupational Safety and Health Administration and the sheriff’s office were investigating.
The victim was not identified Wednesday pending notification of family members.