A 44-year-old man was hospitalized with first-degree burns over a quarter of his body after an incident in Waianae Tuesday afternoon, according to Emergency Medical Services officials.
Paramedics were called to Apana Road just before 1 p.m.
Honolulu fire crews also responded to the scene.
Fire officials say there was a fire from an arc cutter, which is a high intensity torch cutter that cuts through metal and steel.
The man who was injured was working on a pig farm.
Fire officials are not sure what caused the flash fire. Crew could not find a gas leak.