LOS ANGELES — Use of traditional fire suppression tactics and the unrecognized presence of combustible metals factored into an explosion that injured seven firefighters in Los Angeles last year.
The explosion occurred as firefighters were battling a fire that tore through a block of industrial buildings in South Los Angeles on July 13, showering the responders with molten titanium and shrapnel.
The impact from the flaming shrapnel and percussion from sound waves caused injuries ranging from burns to ringing in ears, according to a NIOSH safety investigation report released Wednesday.
When firefighters arrived on scene, an offensive attack was initially implemented, but after about 12 minutes firefighters switched to a defensive attack due to rapidly deteriorating conditions.
About 40 minutes into the response, the main explosion occurred, spreading the fire and resulting in injuries and damage to fire apparatus.
The incident commander realized combustible metals might be present, and ordered firefighters to use unmanned ladder pipes to fight the fire while keeping water away from the burning metals.
Another explosion occurred more than two hours later when water came in contact with burning combustible metals, but no injuries took place.
Special tactics for combustible metal
As a result of the investigation, NIOSH is stressing the need for fire departments to train for combustible metal fire recognition and tactics.
“Combustible metal fires present unique and dangerous hazards to firefighters which are not commonly encountered in conventional structure firefighting operations,” the report said.
“The temperatures encountered in a combustible metal fire far exceed those of a structure fire.”
Using a wet extinguishing agent such as water hose streams accelerates combustible metal fires as the reaction produces highly flammable hydrogen gas, which can lead to explosions.
Instead of water, firefighters should use “a bulk dry extinguishing agent compatible with the product involved, such as dry sand, dry soda ash, or dry sodium chloride,” investigators said.
However, applications of dry agents beyond the initial stage of the fire is typically not feasible, in which case the best approach is to isolate the material as much as possible, protect the exposures and allow the fire to burn out.
“In this incident, several firefighters noticed the unusually bright white hot fire, white sparks, bluish green hues of the fire, and white smoke but did not recognize that this could be indicative of burning combustible metals,” the report said.
The fire department did not suspect combustible materials were present until after the first explosion and a placard indicating oxidizers were present was discovered inside the structure.
NIOSH is also calling for departments to ensure their procedures for combustible metal fires are up to date, since the fire department had an outdated policy calling for copious amounts of water to be put on a metal fire.
“The policy had been based on a training scenario in which burning magnesium Volkswagen engine blocks, when hit with water, would spark, but the water cooled the large mass of magnesium enough to put the fire out,” the report said.
“Numerous fire departments across the country remember this training scenario and have not kept up with the increasing and varied uses of combustible metals in everyday products.”
Further findings
In addition, NIOSH recommends fire departments:
- Ensure that pre-incident plans are updated and available to responding fire crews
- Ensure that first arriving personnel and fire officers look for occupancy hazard placards on commercial structures during size-up
- Ensure that all firefighters communicate fireground observations to incident command
- Ensure that firefighters wear all personal protective equipment when operating in an immediately dangerous to life and health environment
- Ensure that an Incident Safety Officer is dispatched on the first alarm of commercial structure fires
- Ensure that collapse/hazards zones are established on the fireground.