A 5-gallon propane cylinder, stored as a spare barbecue cylinder on the bottom rack of a grill, vented through its pressure relief valve while the grill was in use on a hot summer evening in California. The vented propane ignited in a jet of fire that reached three adults seated at a patio table some eight feet away, and inflicted severe burns on at least one of them. Exponent's investigation of the incident revealed that the cylinder had been significantly overfilled, and that this was a major contributing factor to its venting. Open flames in the grill box, exposed from underneath, likely ignited the vented propane. Exponent performed engineering analyses to estimate just how much the cylinder had been overfilled, and to simulate the rise in temperature, liquid level and pressure that led to the cylinder venting. We also performed a controlled combustion test to demonstrate what can happen when an overfilled propane cylinder is heated and vents in the vicinity of an ignition source.

Fires & Explosions