IAFC updating CO response workshop instructor guide
“Lessons Learned” since the International Association of Fire Chiefs (IAFC) has developed its train-the-trainer workshop for responders to activations of CO detectors will be incorporated in an updated instructor guide. The lessons, the IAFC says, will help increase the effectiveness of responses to these calls.
Following are the five most critical lessons and a summary of the IAFC`s recommendations for responders:
1. CO can be hard to find. When you do not find CO, investigate further. If there is a chimney, locate it from outside the house and determine which rooms are next to it. Check around all walls that form the chase on each floor, including closet walls. Take readings in the attic around the top of the chimney chase. Experience has shown that CO detectors are very reliable. When responders do not find CO, a more comprehensive investigation may be needed. Two fire departments, for example, found CO in a closet by chance. In both cases, the rear wall of the closet was next to the chimney. Cracks in the chimney were leaking CO into the void around the chimney, where it infiltrated the closets and then adjacent rooms.
In another case, a homeowner installed a CO detector that activated the same day. When the investigator could find no CO, the owner assumed the detector was defective and returned it to the store for a refund. The sales clerk insisted the detector had reacted to CO. The owner accepted an exchange detector, which also activated. Again, no CO could be measured. This scenario occurred three times. On the last response, the investigator noted the attic access in the hallway ceiling as he was about to leave. He inserted his meter`s probe into the attic space and got a reading. He found that the furnace`s flue pipe had rusted away at the roof line. The CO would migrate into the home`s living space whenever an air pressure differential pulled air into the house from the attic. The flashing on the roof made the situation appear normal from the outside.
2. Slight changes in conditions can cause CO to concentrate or dissipate. CO detectors that pass the tests in UL 2034 are highly reliable. Investigators are searching for CO concentrations that are only tens or hundreds of parts per million. Lower concentrations dissipate more quickly than heavier concentrations; therefore on nonemergency calls (where no one is reporting symptoms of CO poisoning), responders are more likely to get a lesser or no trace of CO. Air circulation patterns and the infiltration rate of fresh air are among the factors that affect the rate of dissipation. Both are easily changed by opening a window or operating an exhaust fan. Even a sight change in these conditions can dissipate the CO that activated the detector.
Other things investigators should look for are downdrafts (or reverse stacking–a mechanically induced downdraft). A very slight change in conditions can create them and then stop them. Confirming this condition can take much time and patience because a combination of events acts to create downdrafts and the investigator would have to create the same combination to duplicate the situation that activated the CO detector. Keep in mind that the CO concentration that caused the activation may have taken hours to do so (the activation thresholds for CO detectors are a function of CO concentration over time). The concentration can quickly dissipate if the air infiltration rate is changed–by an open window or door, for example.
The best method for finding the cause of the activation is to create a worst-case scenario and then systematically check every potential source. Many CO sources occur in cycles–they are created for a period and then dissipate–which may make it more difficult to recreate the exact conditions that induced the CO concentration that activated the detector.
If the problem is not found during the initial investigation, analyze the conditions that might have triggered the alarm. One way to do this is to place a CO meter with a data logger in the home for 24 to 48 hours to record transient CO concentrations. Determining when they occur and for how long can help to identify the source(s) of the CO.
3. Advising citizens that an activation was “probably a false alarm” carries serious consequences. Doing this may cause citizens to ignore future activations; and, of course, this can lead to grave consequences. If an expanded investigation is needed, the fire department itself can do it or arrange for another agency to do the work.
Another reason for not calling an activation a false alarm is the potential liability to the fire department. Making a statement that cannot be supported by facts can have dire consequences if the investigator is proven wrong by later events. When responding to an activation, ask yourself what can be supported by facts. The facts are (1) A piece of special equipment designed to detect CO has activated; and (2) your meter, also designed to detect CO, does not detect any at that moment. The conclusions that can be drawn are that the CO detector activated without detecting CO or that a CO concentration activated the detector and dissipated before you investigated. There is no factual evidence to support the first conclusion. The only thing you know is that CO was not present when you checked for it. This is a compelling argument against concluding that the absence of CO means there was a false alarm. If you do not find CO, the prudent action is to limit the report to facts and state that nothing was found.
The term “nuisance alarms” also should not be used to refer to calls where CO is detected in levels lower than those currently considered to be harmful because no authority on the subject has defined what a nuisance alarm is. Therefore, anyone using the term will be on his own if challenged. Another reason for not claiming a nuisance alarm is that CO meter readings during an investigation do not tell you the CO concentration time period during which the detector activated. They tell you what the CO concentration was at that time.
4. The fear of a CO explosion when conducting an investigation is groundless, but flammable gas may be a potential problem. CO detectors may react to extremely high levels of gases as if they were CO. (See News in Brief, May 1996, for the discussion.)
5. Public education is extremely effective in managing the CO call load. Educating the public can reduce the number of CO calls, since it can affect the human behavior responsible for a significant number of CO calls. Many detectors, for example, activate because they are installed too close to appliances. The CO concentration is heavier where it leaves its source. If the detector is too close to the source, the detector will respond to that level instead of the ambient level, which the detector is supposed to monitor. The difference between source and ambient CO levels in one study was 47 ppm vs. nine ppm.
Running an automobile in a garage with the overhead door open, even for a very short time, also can raise CO levels. The exhaust from a cold engine can momentarily carry 25,000 to 30,000 ppm, and any delay in moving the car out of the garage increases the CO concentration left in the garage after the overhead door is closed. If the house is under negative pressure, the CO-laden air drawn from the garage can be enough to activate the detector. People should be instructed to back their vehicle out of the garage immediately after starting it to avoid a detector activation and avoid exposure to CO, low levels of which can be harmful to the more vulnerable populations such as infants, small children, the elderly, and those with certain medical conditions.
The IAFC revised instructor guide is available for all who have received the original version. It may be requested by fax at (913) 268-5113.
(Condensed from On Scene, IAFC, Feb. 1 and Feb. 15, 1996.)
