Tis’ the Season – for CO calls

This article is likely being read after the first of the year, but it is being written as we crank up for the Christmas holidays. Tis’ the season for Santa Claus, eggnog, and Carbon Monoxide (CO) calls. Unfortunately, the potential for CO calls does not end with Santa’s return to the North Pole.


Carbon Monoxide calls will continue to be more frequent throughout the winter months. Each year, over 100 people die from CO produced from non-automotive consumer products. Carbon monoxide (CO) is often a byproduct of incomplete combustion. It is dangerous to us during overhaul at structure fires, but our customers also derive it from very unique methods. Quite often, portable generators running inside or too close to the home produce CO. There have been incidents of persons using charcoal grills inside of homes, which cause dramatically high levels of CO build up. A wood burning stove can cause a CO buildup if the ventilation piping is defective, improperly installed or fails. Even gas logs or a fireplace can cause a CO call from incomplete combustion or improper ventilation. Most of our customers do not have CO detectors, which means we will likely not be dispatched to a CO call necessarily. Instead, we are likely to be dispatched to someone that is displaying the signs and symptoms of CO poisoning. They have a headache, they are dizzy, they are nauseous and they may be vomiting. Here is the big sign that this is a CO call. The rest of the people in the building are having similar signs and symptoms. Of course, you want to consider the location and the fact that this could be something other than CO.  Running a multi-gas meter with a CO sensor through the building will give us the definitive result.

Carbon monoxide is both toxic and flammable. It is colorless, odorless, tasteless, and is toxic by both inhalation and absorption. Normally, at a hazmat call where we have a product that is toxic by inhalation and skin absorption, it demands that we utilize the highest level of respiratory and skin protection available, namely Level A. At CO calls, however, we frequently use structural PPE and SCBA. This is because CO also has a fairly broad explosive range. The lower explosive limit is 12 percent and the upper explosive limit is 75 percent. There is a narrow range where the concentration of CO in air is either too lean or too rich to burn. Carbon Monoxide has a vapor pressure of 1.55 x 10+8 mm Hg at 25 degrees Celsius. Remember when it comes to these exponents in the hazmat world, DSTU  — Don’t Screw This Up.  When doing the math, 1.55 x 10+8 is equal to 1.55 while moving the decimal eight places to the right. So, the vapor pressure of CO is 155,000,000 millimeters of Mercury at “room temperature.” Recall that our old friend Chlorine, which we rarely see outside of its container as a liquid, has a vapor pressure of 7,600 mm Hg. The vapor pressure of CO is over 20,000 times higher, which means we will probably never see it as a liquid. As a gas, CO has a vapor density of 0.968, which is slightly lighter than air. The time weighted average (eight-hour) is 25 parts per million (ppm), and the level at which it is immediately dangerous to life and health (IDLH) is 1,200 ppm. This is only 0.12 percent concentration in air — remember, the air we breathe is 20.9 percent oxygen. While we would need between 120,000 ppm and 750,000 ppm to be in the explosive range, tests have shown that as little as 5,000 ppm can be fatal to a human in five minutes. If you pulled up to a fixed facility with an NFPA 704 placard on it, the placard would have a red 4, blue 3, and 0 yellow, with a blank white diamond. Given the broad explosive range, CO demands an extreme flammability rating, but do not let the yellow 3 fool you. It represents a serious health hazard and will be fatal in toxic concentrations long before it reaches the lower explosive range. 

We can use our CO sensor in our multi-gas meter to measure the presence of CO, but there are a couple of caveats with that. First, most CO sensors will not likely measure fatal levels and very few, if any, will measure levels through the explosive range.  Moreover, in the absence of a CO sensor, we probably cannot rely on our photoionization detector (PID) to detect CO. The ionization potential of CO is 14.01 millivolts (eV). Because most of us use 10.6 eV lamps in our PIDs, they are not strong enough to ionize and measure CO. Therefore; we can only use our multi-gas meters to detect the presence and relative amount of CO. If our monitor shows below 25 ppm, we should try to determine the source of the CO and advise the occupants that they may be temporarily displaced. For levels above 50 ppm of CO, we should evacuate the occupants immediately. 

Anyone exposed should be evaluated by an advanced life support provider.  Hemoglobin is the protein molecule in the body that normally carries oxygen. Carbon Monoxide has a 250 times greater affinity for hemoglobin than oxygen. This means that in a high CO atmosphere, our red blood cells will not be carrying oxygen to the cells of our body. Instead, they will carry carbon monoxide. This results in cellular injury and/or death, which can cause organs to fail and eventually can be fatal. Because the brain and the heart have the highest oxygen demand, you will notice changes there first.  Interestingly, if we put a patient with CO poisoning on a pulse oximeter to measure their SpO2, we will find that it is normal — 98-100 percent. This is due to the pulse oximeter measuring the oxygen molecule in Carbon Monoxide just as it measures the oxygen molecule in the air we normally breathe (O2). In high exposures, there are also neurocognitive effects, such as dementia, psychosis, neuropathies, and personality changes that can occur up to 40 days after exposure. All patients that have been exposed to any level of CO should be rapidly transported to the closest appropriate medical facility. CO is teratogenic and because the placenta is not very good at filtering CO, a fetus is much more vulnerable to CO poisoning than the mother. Although mom may not be demonstrating very many signs or symptoms, you should rapidly transport her in order to insure there was no damage to the baby. Some references recommend the use of hyperbaric oxygen therapy for carbon monoxide poisoning, particularly among the pregnant, so you should be familiar with where the closest facilities are providing emergent hyperbaric services. Obviously, those with pre-existing medical conditions — COPD, anemia, and heart disease — are at a higher risk of injury and death than healthy adults.

Finally, it will be necessary to mitigate the source of CO, render the scene safe, and return the property to the owner/occupants. This often involves utility companies who are the technical experts at an incident such as this. Insure that they, too, are properly protected. Ventilation will aid in rendering the scene safe, but take caution if gas powered positive pressure ventilation fans will be used. They can be beneficial when very high levels of CO are present, but gas powered fans blow the exhaust from their motors into the building also. A point will be reached where the fan will be putting more CO into the building than it is taking out. At that point, natural ventilation may be preferred. Continue to monitor the atmosphere until it is completely safe and insure that our customers have somewhere to go if they are evacuated. I hope everyone had a safe and merry Christmas and happy holiday season.

Be safe and do good.

David Greene has over 20 years experience in the fire service and is currently the Assistant Chief with Colleton County (SC) Fire-Rescue. He is currently working on his PhD through Oklahoma State University. He is a certified Executive Fire Officer through the National Fire Academy, holds the Chief Fire Officer Designation and is an adjunct instructor for the South Carolina Fire Academy. He can be reached at dagreene@lowcountry.com.

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