The man was using electrical current to separate hydrogen from water in a two-story shed in Kendall, east of Lynden, when an improvised container, a five-gallon propane tank used to store it, over-pressurized and exploded.
The blast shook the entire neighborhood.
He suffered severe burns on his arms and legs and chest and was airlifted to Harborview Medical Center.
The explosion blew apart parts of the shed, but there were no other homes damaged or other people injured.
Police say the explosion appears to be an accident and no crimes were committed.
The FBI, the Bureau of Alcohol, Tobacco and Firearms, the Washington State Patrol and the Bellingham Police Department’s Hazardous Devices Unit are all assisting with the investigation.