The largest cylindrical gas container in the world in 1927 was in the heart of the industrial center of Pittsburgh, Pennsylvania. On the morning of November 14, 1927, it developed a leak, so repairmen set out to look for it….
….with an open-flame lamp.
At 8:43 a.m., either they found the leak, or the leak found them.
The tank, containing 5 million ft3 of natural gas, rose in the air like a balloon and exploded. Chunks of metal, some weighing more than 100 lbs, were scattered great distances, and the combined effects of air pressure and fire left a square mile of devastation. Twenty-eight people were killed and hundreds were injured. The sound of the explosion was heard 20 miles away.