St. Louis was experiencing a heat wave with bright sunlight and temperatures reaching 97 °F (36 °C) on June 24, 2005. Praxair operations proceeded normally during the morning and early afternoon; however, about 3:20 pm, a technician retrieving cylinders from an outside storage area saw a ten-foot high flame coming from a cylinder and activated the fire alarm. Security camera video from the facility shows the release and ignition of gas from a cylinder in the propylene return area.

As workers and customers evacuated, the fire spread to adjacent cylinders. Security camera video shows nearby cylinders igniting in the first minute. At 2 minutes, cylinders begin exploding, flying into other areas of the facility, and spreading the fire. After 4 minutes, the fire covers most of the facility’s flammable gas cylinder area and explosions are frequent.

KEY ISSUES:
• HIGH AMBIENT TEMPERATURES
• RELIEF vs VAPOR PRESSURE
• FLAMMABLE GAS DETECTION
• DELUGE SYSTEMS
• FIRE BARRIERS

ROOT CAUSES:
• Although the official cause is undetermined, the most likely cause was ‘propylene venting due to the prolonged exposure to excessive heat’

Image credit: CSB