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- Consider where the contaminated atmosphere will be sent. Sending a contaminated atmosphere somewhere else is irresponsible until it can be absolutely verified. Responders need to thoroughly check where contaminants will travel and even consider verification through competent air-monitoring operations.
- Consider how the exhaust openings will be made before ventilation begins. Usually, doors and windows can be used as exhaust points for contaminated atmospheres, but there may be times when there is no natural opening for exhaust. Exhaust openings may need to be made and can be accomplished in van trailers, wood-frame buildings and other lightweight structures by making artificial openings. For rooms inside buildings with only one door, blowers can be set up to blow fresh air into the lower half of the door while the top of the door acts as the exhaust point. This setup would also require another blower to be set-up outside the structure to blow fresh air out of the building's exhaust point.
- Consider where the blowers must be set up to ventilate effectively. This requires coordination and communication with all ventilation crews before actual PPV deployment. Also consider the minimum PPE to be self-contained breathing apparatus (SCBA) and structural fire protective clothing (SFPC) for personnel who deploy blowers in the "hot zone."
- Consider how to safely start the blowers. When approaching the object to be ventilated, it is imperative to be on the upwind side and to use monitoring instruments to check for flammable gases. Blowers should be operated only in safe atmospheres and without risk of igniting atmospheres. Even after blowers are started, they should be constantly checked for continued operation in safe atmospheres. An option for PPV application is to attach flexible ventilation chutes or even disposable plastic tubing to the blowers to better focus the ventilation efforts and also keep each blower in a safe location.
- Consider controlling the ventilation rate. If interior spaces are filled with unwanted atmospheres that may be flammable, corrosive and/or toxic, releasing them to the outdoor open environment may cause exposure problems for the public. For this reason, consider releasing the unwanted atmosphere a little at a time in order to keep contaminants below safe exposure thresholds. Use appropriate monitoring strategies to assure that downwind contaminants are at safe levels. This strategy may take more time than you would like, but it may be the safest action.
- Consider ventilation as a means to creating a micro-climate. In order to control working within vapor clouds, it may be better to avoid being in the cloud in the first place. Consider using a blower to ventilate a work area of gases and vapors and increase visibility yet decrease risk. One example is to use a blower on the ground and directed to disperse vapors while working around a railcar's manway.
Essentially, PPV for hazmat response is smart in that it controls dangerous and unwanted atmospheres. It is creating a micro-climate that can better protect responders, helping to avoid use of bulkier PPE and carrying numerous and unnecessary air monitors, and it can also better protect exposed populations. Consider this tool at every hazmat event and with the precautions cited above, and use it intelligently.
DAVID F. PETERSON is a lieutenant in the Madison, WI, Fire Department, where he is the lead fire and hazmat training officer. He is in his 30th year as an emergency responder and is the managing member for the Wisconsin FLAME Group LLC. Peterson also operates www.hazmatpetie.com, a hazardous materials response training website. Please send your comments and questions to him at www.hazmatpetie.com or email@example.com.