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Haz Mat "Specialist Course"
« Foam 107.2 Application Techniques | Main | Foam 105.2 - Foam Proportining »

Foam 106.2 Discharge Devices and Nozzles

Air aspiration is paramount in the formation of a proper “Bubble.” It is this structure that affords the firefighter, when properly constructed, to suppress fires, eliminated hazardous vaporization, and eliminated the immediate need for large scale evacuation of “affected” persons. An “Affected” person is terminology that directly refers to civilians in the nearby area of the spill that are untrained residents or business workers that can quickly be negatively affected by these hazards. For Fire Departments and Haz Mat Teams, the ability to quickly evacuate these persons has multiple difficulties for obvious reasons. Manpower, transport vehicles, and evacuee destination location medical needs, are some that top the list. All these complicate your resources and lengthen the time to mitigate an incident.

Low to medium aspiration nozzles or devices are usually sufficient for flammable liquid fires but not for hazardous material vaporization control. For this tactic medium to high aspiration nozzle devices must be used. This is critical for your choice to eliminate the need of immediate evacuation. Choosing the correct device will allow you to “shelter-in-place” “affected” persons reducing your manpower needs and decreasing the incident mitigation time overall. Because you can now concentrate on spill mitigation as opposed to civilian evacuation concerns.

Low aspiration nozzles construct a smaller, wetter, bubble. This bubble absorbs more ambient heat from a flammable liquid fire while still able to hold its structure affording vaporization control over the remaining flammable liquid preventing re-ignition and subsequent “burn-back” resulting in a continued flammable liquid fire. Medium aspirated devices produce a larger “dryer” bubble. This bubble is better for vaporization control as it floats longer, and holds its structure as long as not subjected to flame. Here, the vaporization control time is longer without replenishment and affords confident hazardous material mitigation techniques and longer time frames that are associated with this discipline. 

The choice and or adaptability of your air aspiration nozzle device can yield you desirable or undesirable results depending on which is chosen. Expansion rates (Foam 106) are critical understanding for making this choice. They reflect the mathematics of “how” the air aspirating nozzle or device is functioning. Always refer to these Foam standards under the NFPA 11 section dealing with air aspiration for the appropriate choice.

The number 1 concept to understand is; for proper extinguishment, vapor control, smothering, and elimination of off-site evacuation, Finished Foam MUST be ASPIRATED in order to perform. Without aspiration, large quantities of Foam concentrate shall be wasted without success in extinguishment or vaporization mitigation. Choose wisely, your incident will depend upon it.

   Haz Mat Mike


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