San Juanico – 1984

If you’ve got a storage and distribution terminal containing a third of Mexico City’s liquid petroleum gas (LPG) supply stored in 54 tanks, it pays to buy the best gas-detection system money can buy. Unfortunately, the San Juanico facility had the tanks – filled with a mixture of butane and propane – but lacked a sophisticated gas-detection capability.

Early one November morning in 1984, as the surrounding town of San Juan Ixhuatepec slept, a pipeline ruptured during a transfer procedure. An insidious cloud of heavier-than-air LPG accumulated and slowly travelled towards die western end of the site, where a flare pit burned off waste gas. Naked flame and a huge pool of flammable gas are a lethal combination.

The startled residents of San Juan Ixhuatepec were awoken by a massive explosion, which was followed by an intense fire fed by gas escaping from blast-damaged tanks. A few moments later, the next detonation in a percussive hour-long series took place as individual tanks went up. These were BLEVE explosions, the bland acronym standing for Boiling Liquid/Expanding Vapour Explosion. Each blast contributed more burning gas to the conflagration and when two of the largest spherical tanks blew, seismic instruments registered 5.0 in the Richter scale – equivalent to a moderate earthquake. The terminal would bum for over 24 hours.

It soon became apparent that this catastrophic event was not only the worst LPG accident ever recorded, but also one of the worlds worst industrial disasters. San Juan Ixhuatepec – mainly consisting simple one-storey concrete houses with tin roofing – was devastated by blast waves, flying debris and a deadly firestorm. Hundreds of the 40,000 inhabitants died and many thousands were badly injured. Casualty figures were vague because the vast majority of the dead were reduced to ashes as the inferno raged.

When: November 19 1984

Where: San Juan Ixhuatepec, Mexico

Death toll: Estimates put the death toll at 500 to 600, with perhaps 6,000 to 7,000 severely injured.

You should know: Mexico’s state-run petroleum company, the giant PEMEX energy combine, owned the San Juanico facility. In true ‘not our responsibility’ style, the company initially tried to suggest that the disaster was initiated not by its own negligence but an explosion in a nearby factory.