An ammonium nitrate fire is difficult to fight.
Fire retardants that focus on excluding oxygen have no effect as the nitrate part of the molecule, which consists of one nitrogen and three oxygen atoms, provides all the necessary oxygen.
The only effective control is to remove the heat, which causes the explosive reaction, by flooding the area with water.
But it’s unknown if the firefighters who responded to the initial fire were even able to commence a water flood before the explosion, which happened minutes after they arrived.
Fire fighting is further complicated by the presence of other hazardous chemicals used to make the fertiliser, principally anhydrous ammonia (liquefied ammonia gas) and nitric acid.
The firefighters on the scene quickly assessed that they could not put out the fire, they then immediately switched to warning and evacuating nearby residents.
From the “Emergency Response Guide” (this little D.O.T orange book is on nearly every piece of fire and EMS apparatus in the country:
ERG GUIDE 140 - OXIDIZERS
POTENTIAL HAZARDS
FIRE OR EXPLOSION
- These substances will accelerate burning when involved in a fire.
- Some may decompose explosively when heated or involved in a fire.
- May explode from heat or contamination.
- Some will react explosively with hydrocarbons (fuels).
- May ignite combustibles (wood, paper, oil, clothing, etc.).
- Containers may explode when heated.
- Runoff may create fire or explosion hazard.
HEALTH
- Inhalation, ingestion or contact (skin, eyes) with vapors or substance may cause severe injury, burns or death.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may cause pollution.
PUBLIC SAFETY
CALL Emergency Response Telephone Number on Shipping Paper first. If Shipping Paper not available or no answer, refer to appropriate telephone number listed on the inside back cover.
- As an immediate precautionary measure, isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters (75 feet) for solids.
- Keep unauthorized personnel away.
- Stay upwind.
- Keep out of low areas.
- Ventilate closed spaces before entering.
PROTECTIVE CLOTHING
- Wear positive pressure self-contained breathing apparatus (SCBA).
- Wear chemical protective clothing that is specifically recommended by the manufacturer. It may provide little or no thermal protection.
- Structural firefighters’ protective clothing will only provide limited protection.
EVACUATION
Large Spill
- Consider initial downwind evacuation for at least 100 meters (330 feet).
Fire
- If tank, rail car or tank truck is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions.
EMERGENCY RESPONSE
FIRE
Small Fire
- Use water. Do not use dry chemicals or foams. CO2 or Halon? may provide limited control.
Large Fire
- Flood fire area with water from a distance.
- Do not move cargo or vehicle if cargo has been exposed to heat.
- Move containers from fire area if you can do it without risk.
Fire involving Tanks or Car/Trailer Loads
- Fight fire from maximum distance or use unmanned hose holders or monitor nozzles.
- Cool containers with flooding quantities of water until well after fire is out.
- ALWAYS stay away from tanks engulfed in fire.
- For massive fire, use unmanned hose holders or monitor nozzles; if this is impossible, withdraw from area and let fire burn.
SPILL OR LEAK
- Keep combustibles (wood, paper, oil, etc.) away from spilled material.
- Do not touch damaged containers or spilled material unless wearing appropriate protective clothing.
- Stop leak if you can do it without risk.
- Do not get water inside containers.
Small Dry Spill
- With clean shovel place material into clean, dry container and cover loosely; move containers from spill area.
Small Liquid Spill
- Use a non-combustible material like vermiculite or sand to soak up the product and place into a container for later disposal.
Large Spill
- Dike far ahead of liquid spill for later disposal.
- Following product recovery, flush area with water.
FIRST AID
- Move victim to fresh air.
- Call 911 or emergency medical service.
- Give artificial respiration if victim is not breathing.
- Administer oxygen if breathing is difficult.
- Remove and isolate contaminated clothing and shoes.
- Contaminated clothing may be a fire risk when dry.
- In case of contact with substance, immediately flush skin or eyes with running water for at least 20 minutes.
- Keep victim warm and quiet.
- Ensure that medical personnel are aware of the material(s) involved and take precautions to protect