Bring Me That Thing That Beeps a Lot: Air Monitoring 101

As you monitor, you need to slow down

By Alexander Oliver

Why do we focus so much on-air monitoring? We all have experienced the 4 a.m. carbon monoxide alarm that roused everyone from that ever-so-elusive good sleep at the station or a warm comfortable bed from home for volunteers. However, when the apparatus arrives on scene, you are the air monitor expert. Your fire department is qualifying that environment’s air as either safe for human occupancy or potentially dangerous. Qualifying the environment is a major responsibility. Your department inherits the liability for whatever outcome may happen in terms of air quality decisions. Think of it like this: What if it was your parent’s or grandparent’s home? You would want the responding fire department to be well versed, knowledgeable, and professional in their air monitoring skills and assessment. This service we provide to the public is one that unfortunately gets glossed over but is a vital function. Here are some easy tips that could help improve your fire department’s air monitoring.

First, let’s look at how the air monitor works. I could tell you about the inner workings of the internal sensors, but let’s keep this straightforward. Each sensor essentially ionizes (or charges with energy) the air as it passes through the sensor. The monitor records a change in the total charge for that sensor, applies mathematical algorithms, and then displays a value on the monitor screen for the user to see. This process is not instantaneous.  It takes time for these series of steps to take place. Based on the manufacturer of your air monitor sensor, this could be anywhere from 15 to 30 seconds. Always reference your manufacturer’s guidelines when trying to discover this “processing” time. 

So, what does all this mean for the firefighter using the air monitor? This means that as you monitor, you need to slow down. Taking a reading in one location might take 45 seconds before you move onto the next location. Far too often, firefighters walk through a space fluidly without pause while they air monitor. This style will not yield you accurate results. Allow for that “lag” time to pass and give the air monitor time to display the most accurate reading. 

Next, figure out where to monitor the air. Use the acronym “ABC”: The “A” stands for above.  Hold the monitor above your head and check the atmosphere above you. Check for those gases that are lighter than air, like natural gas. The “B” stands for below. Hold the monitor below your waist and check for those gases that are heavier than air (which most are), like propane. “C” stands for center or chest. Check at chest or center level for gases that have a vapor density close to one (air’s vapor density), like carbon monoxide. To quickly refresh some basic physics knowledge, vapor density tells us where to find the gas in an environment compared to air. Air has a value of one.  If the vapor density is greater than one, that gas is heavier than air and will sink. This gas will act like a liquid. It will collect in low-lying areas and follow the path of least resistance. Chlorine and propane are good examples of common gases heavier than air. If the vapor density is less than one, the gas is lighter than air and will rise. These are the gases that will dissipate into the atmosphere if outside or collect at the ceiling if enclosed. Natural gas and nitrogen are good examples of gases lighter than air. If the number is close to one, that gas will mingle with the air and travel where the air travels in that compartment. Carbon monoxide has a vapor density of .968, very close to the value of air; thus, carbon monoxide will behave in a house, for example, as normal air currents do for that home.

What personal protective equipment (PPE) is appropriate for air monitoring?  Now, the on-scene situation and your departmental standard operating procedures will give you a firm base to go from, but for most air monitoring calls, turnout gear is usually enough and an appropriate level to begin with. Far too often, firefighters don’t take the idea of airborne exposure seriously for air monitoring calls and don’t wear any protective gear or respiratory equipment. Even something we encounter every day like carbon monoxide can be harmful and deadly in high enough exposures. In the process of air monitoring, all firefighters should wear an air pack. The most common route of exposure for firefighters is through inhalation. Wearing an SCBA pack and mask provides the maximum protection for our respiratory tract and can easily mitigate the main hazard for most air monitoring calls. Turnout gear provides moderate protection for a wide range of environments, but don’t let that gear lull you into a false sense of security. Use on-scene clues to determine if your PPE selection is adequate for the task at hand.

When should we mask up? The answer should be muscle memory, always! Don’t wait for the air monitor to tell you that the atmosphere is bad and that you already have exposed your airway to a potentially harmful gas before you mask up. At that point, the potential damage could already be taking place in your lungs and the exposure is complete. Remember, there is a delay for air monitoring. The air must get pulled into the sensor from the pump, measured across the sensor, then provide the user with a value to recognize. By the time all this takes place, the user could have had a significant exposure amount depending on the gas product. Wear your air pack and mask up every time; wait for the air monitor to tell you the atmosphere does not contain any abnormal gas values. Then, with proper ventilation (if needed) in place, you can remove your air pack safely.

When operating the air monitoring device, make sure you bump check your equipment prior to entering an atmosphere. Make sure that it knows what limits to alarm at with this bump check.  Provide the monitor with a fresh air calibration prior to entering the unknown atmosphere as well. Let the sensors know what normal air values are. Avoid doing the fresh air calibration in the cab of a fire truck. There could be gases in the cab that could alter what you want the monitor to know as fresh air. Gear could be off gassing from a structure fire or there could be a minor exhaust leak. These would impact your fresh air calibration numbers. 

Lastly, bump check the monitor after the incident. This helps us make sure that the sensors didn’t get exposed to an atmosphere that made them not work correctly in the course of operations.  With all these steps, and the air monitoring itself, record all the data. Document all these steps at each incident that you operate your air monitor. This documentation could be useful for quality control measures or if the fire department must testify about an incident where the air monitor was used.

Air monitoring is a vital function that fire departments employ across the nation. You are the qualified expert on scene if you are the person operating the air monitor. Take your time. Use the ABCs of air monitoring to carefully inspect the environment atmosphere for gases. Make sure that you take time to take readings at all three levels of the ABCs. By taking your time, you allow for those delays in the process to pass and allow the monitor adequate time to provide you with accurate readings of the atmosphere. When using an air monitor, wear the appropriate PPE and full SCBA with mask and air on. Don’t risk your health by waiting for the air monitor to alarm at you before you turn on and use your SCBA. By then, it will be too late, and the exposure already has taken place. Mask up before entering any unknown atmosphere. Protect your airway and your health! Finally, bump check your air monitor before and after use to make sure that the sensors are operating correctly for the incident. Then document all steps and findings for departmental records.

Alexander Oliver is a senior firefighter, a hazmat technician, and an EMT-Basic for the Raleigh (NC) Fire Department.