Butane, one of those bastard gasses. ~ Hank Hill
Firefighters.. Thanks!
Since butane has very low head pressure at room temperature (10-15 psi), I wonder how they had a failure of that size? Storage tanks for butane are rated at 250 psi.
Unfortunately, butane is delivered without mercaptain odorizer, so leaks in plumbing are easy to miss. Maybe their process was running unattended? Obviously they had no carbon detectors in the building, which will result in huge fines.
(Propane and butane bulk transport Is my business...)