Ice & Oxygen Create Hazmat Problem In Iowa

OXFORD FIRE DEPARTMENT Chief Mark Hora Personnel: 24 volunteer firefighters Apparatus: One pumper, two tankers, one brushfire rig, one personnel response van, one medical first responder vehicle Population: 600 Area: 100 square miles An...


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Once Suedkamp and the Johnson County Hazmat Team were on scene, he moved the Oxford firefighters back from their location within 30 feet of the Cryogenic trailer to a position 300 feet away as recommended in the 2000 Emergency Response Guidebook. In so doing, Oxford firefighters abandoned an engine that was parked close to the accident.

From that point, emergency responders were sequestered to waiting for Cryogenic company officials and heavy equipment to arrive on scene. The tanker was later set on its wheels using cranes and towed away.

Hora had a school bus brought to the scene for emergency responders to stay in during the long wait. At 27 degrees, this was also one of the coldest days of the year so far.

Emergency responders operated with all due regard for safety in this incident by conducting a rapid extrication and withdrawing a safe distance away. However, the nature of hazards associated with LOX point out how contrary the element can be to its normally harmless, life-sustaining state.

Ken Humphries, safety director for Cryogenic, explained that LOX itself presents three safety hazards to emergency responders:

  1. As a cryogenic liquid, LOX is stored at a temperature of minus 297.35 degrees Fahrenheit. Contact with the cryogenic liquid or cold piping containing the liquid can cause tissue freezing or frostbite on dermal contact or if splashed in the eyes.
  2. Breathing high concentrations of LOX (greater than 75 molar percent) causes symptoms of hyperoxia, which include cramps, nausea, dizziness, hypothermia, ambylopia, respiratory difficulties, bradycardia, fainting spells and convulsions capable of leading to death. In general, pure oxygen is a local irritant to mucous membranes and, with extended continued exposure, can be destructive to lung tissue.
  3. LOX splashed onto an emergency responder's clothing or protective gear, or an emergency responder coming into contact with a LOX vapor cloud can cause the emergency responder's clothing to become oxygen-saturated. The danger with such a situation is that if they were to contact an ignition source, there could be a flash fire resulting in severe flesh burns or death.

LOX will vaporize slowly once it is introduced into the atmosphere. The fact that this occurs slowly, and not immediately, gives occasion for other hazards while the product remains in its liquid state. Oxygen will react with most materials in one way or another, and this creates special concerns. All easily combustible materials, especially hydrocarbon oils and greases, must be kept from contact with products with high oxygen concentrations, such as LOX. Therefore, Humphries maintains that firefighters would not want to wash away LOX not knowing what, if any of these materials are present in the environment. It is best just to leave the material where it is and leave it alone, it will eventually dissipate.

In the event LOX is spilled over asphalt or other surfaces contaminated with combustibles such as oil-soaked concrete or gravel, or comes into contact with any hydrocarbon such as oil, grease, alcohol, coal dust or gasoline, it could burn with nearly explosive violence if ignited. Such a source of ignition may be an impact or shock, heat or static discharge. In effect, then, the product becomes what Suedekamp, who commanded the hazardous materials sector for this incident, refers to as a "contact explosive" when it is spilled onto pavement.

The Compressed Gas Association recommends if there is a spill of LOX on the pavement, not to walk on or roll equipment over the area for at least 30 minutes after frost from the LOX has disappeared.

To the emergency responder's benefit, trailers used to transport liquefied oxygen are built to Compressed Gas Association Specification 341. They are equipped with three safety features:

  1. A manual vent valve that communicates directly with the pressure side of the trailer. Its purpose is to vent the internal tank pressure. This was the valve opened by the Oxford firefighters when they arrived on scene. The manual vent valve is opened to relieve the pressure down to the desired pressure. Then the valve is closed.
  2. The main safety valve is an automatic self-closing valve that is set to relieve itself when the internal tank pressure reaches 38 psi and will re-seat itself once the pressure is less than 38 psi.
  3. A bursting disc that is set to open up at approximately 57 psi. Once the bursting disc ruptures at the designed pressure, the product will continue to vent until all of the liquid oxygen is released and vaporized, thereby protecting the inner tank from internal pressure damage. This valve does not re-seat itself.