NORWALK FIRE DEPARTMENT
STANDARD OPERATING PROCEDURE
TITLE: CO and HCN Monitoring at fires
DATE: October 22, 2009
To protect the health of all suppression and support personnel at the scene of a working fire, atmospheric monitoring will be performed.
Hydrogen Cyanide (HCN) and Carbon Monoxide (CO) are both potentially deadly gases and by-products of combustion that are present at every structure fire and vehicle fire. HCN is produced when synthetic materials are burned and heated. CO is produced by incomplete combustion. The symptoms mirror each other, so individual monitoring for both gases is needed.
Scope and Procedure:
Properties of HCN and CO:
- CO is a colorless, lighter than air gas with no odor. CO presence cannot be determined unless a gas monitor is used.
- HCN is a colorless gas or bluish/white liquid with a bitter almond odor. (NIOSH). The properties of HCN in the structure fire environment will be completely masked by the smoke.
- HCN and CO are both slightly lighter than air, but will linger in the closed environment.
PPE and Safety:
- HCN and CO exposure may include headache, nausea, fatigue, and dizzy spells at low levels. They will cause respiratory problems, unconsciousness, and cardiac arrest at high levels. Both HCN and CO are flammable gases that will contribute to rollover and flashover.
- Inhalation is the primary route of exposure for both products, so SCBA shall be worn in the presence of any smoke condition, including but not limited to kitchen and cooking fires.
- Skin absorption is a secondary route of entry for HCN. Turn out gear will help protect the HCN from entering through the skin. Turnout gear will hold HCN in the material, so the gear should be washed regularly after structure fires.
Atmospheric monitoring for HCN and CO will be performed before members are allowed to remove SCBA at:
- All structure and contents fires
- Vehicle or other fires in enclosed areas, such as a parking garage.
Turnout gear monitoring should be performed for any fires that exposed members to a sustained smoke atmosphere such as:
- Rubbish fires
- Vehicle fires
Each company has the meter capability to do CO monitoring.
Rescue 2 and both truck companies have the meter capability to monitor HCN.
If there is an incident, and a HCN monitor is not on scene, the incident commander should request one.
The action levels for the monitoring and levels that would allow removal of SCBA are:
- Carbon Monoxide: less than 35 PPM (NIOSH REL)
- Hydrogen Cyanide: less than 5 PPM (NIOSH REL/STEL)
These are not levels to allow residents back into the structure, that should be (0) zero.
Monitoring should continue throughout the entire time companies are operating with out SCBA.
It is the responsibility of the IC and/or the Safety Officer, to ensure that monitoring occurs and the above procedures followed.
Any personnel experiencing the following conditions should be transported to the hospital. The hospital should be made aware of the potential CO and cyanide exposure.
- Exposed to a HCN level above IDLH (50PPM)
- Exposed to a CO level above IDLH (1200PPM)
- Signs and symptoms of exposure:
Officers should complete the proper reporting documentation, including exposure form, CIRMA form, and NFRIS personnel casualty form.
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