An Unusual Carbon Monoxide Call

BY KAYLA WILSON

FIRE DEPARTMENTS across the United States respond to routine carbon monoxide (CO) alarms all the time. Usually, detectors identify well-below-dangerous levels of gas, so residents don’t face a significant life safety risk. But sometimes we get complacent. These calls can have unanticipated consequences and offer lessons learned.

A Seemingly Routine Call

On July 6, 2024, at about 2300 hours, we were dispatched to the report of a CO alarm at a local hotel. We started our gas detectors as we left the firehouse. When we arrived on scene, we grabbed our necessary tools: a gas monitor, water can, and irons. We started our investigation.

The front desk clerk reported that it was just another false alarm, possibly caused by a pilot light going out. We wanted to rule out the natural gas leak he suspected (an obvious life hazard), so we monitored it without any positive readings. Air monitoring in the lobby area read zero for CO, but as we started working our way down the hallway of the hotel, our monitor started to pick up small levels of CO around five parts per million (ppm). Just as we entered the room where the alarm went off, our monitor went into alarm for the following:

CO: 130 ppm.
Methane: 4.3% lower explosive limit.
Hydrogen sulfide (H₂S): 5 ppm.

Hot Pot Hot Spot

Upon further size-up in the room, I noticed two self-heating hot pot meals on the nightstand. And I saw that the fan in the bathroom was on. These observations increased my suspicion about the main culprit for this call. The fan was drawing the gases generated from the self-heating meals toward the room entrance. We instructed the occupants of the room to exit and vented the room with an electric fan after finding no other reading throughout the remainder of the hotel. After we vented the room, the levels went back to normal. As the meals were no longer releasing gas, we left the meals in the room and informed the occupants not to prepare meals in hotel rooms.

Following a Hunch

Immediately after the call, I was interested in the readings on our monitor. Specifically, I wanted to understand why a self-heating hot pot meal would cause a CO alarm to activate. At FDIC 2023, I sat in on a class called “Tactical Response to Explosive Gases,” taught by Jerry Knapp. We have had some bigger events in West Yellowstone caused by explosive gases, so his class really stood out to me. As a result of FDIC, Chief Knapp came out to West Yellowstone and delivered his class to our department.

I reached out to him with my questions about the reasons for these air monitoring readings. We both went down a rabbit hole, trying to understand more. The after-action review (AAR) question stuck out to me: Are we putting ourselves in an immediately dangerous to life or health (IDLH) environment and not realizing it because it’s something odd? Is there something better we can do next time we get a call like this (photo 1)?

1. A recent propane explosion leveled a motel building in West Yellowstone. *(Photo by author.)*

Researching the Source

After some research, I learned that the selfheating hot pot meals in West Yellowstone are like the military’s meals ready to eat (MRE). Here is how to distinguish between commercial self-heating meals and MREs:

In 2019, a study was shared through the Shanghai Daily, where tests on these selfheating hot pot meals were conducted. By analyzing 20 self-heating hot pot products that were purchased online and in stores, the tests recorded readings of temperatures, gas discharge after activation, and the contents of the heating packs. “Tests found that the heat packs discharged hydrogen, a combustible gas,” said Shang Zhaocong, deputy director of the National Chemical Product and Quality Supervision and Testing Center. “The amount of hydrogen was huge. A pack of hot pots generates about 40 liters of hydrogen.”

So, if these hot pot meals produce hydrogen, why were we getting CO, natural gas, and H₂S readings on our gas monitor? The sidebar “A Similar Scenario” answers these questions as it describes a different incident with many similarities to this one.

A Similar Scenario

BY JERRY KNAPP AND JEFFREY DIMETRO

On July 22, 2024, the Highland (NY) Fire Department was dispatched to a CO alarm at a local manufacturing facility that made lighting fixtures. The plant uses a water jet to cut aluminum sheets into components for their fixtures. A water jet cutting tool uses super-high-pressure water and a garnet/sand mixture to cut metal into prescribed, computer-controlled shapes. The aluminum sheets are clamped in place under the water, and the high-pressure nozzle operates under the water and above the aluminum to be cut. This minimizes noise and splash. The way it works is similar to the way a sand blaster works.

Highland Fire District officers and members responded and conducted a size-up. Although this was a manufacturing occupancy, there was no apparent cause for the activation of the fixed/wall-mounted CO detectors. Occupants were asymptomatic. Then members noticed a few small bubbles coming up from the sludge, like debris in the bottom of the water jet tank, which was about 24 inches deep and 3 x 6 square feet. When members put the four-gas meter near the water, CO readings spiked immediately to 100 ppm. Moving the instrument away reduced the readings until it came back near the water surface.

After some research, we learned that the freshly cut aluminum could oxidize in the presence of water and liberate hydrogen. Like the heater meals mentioned in the main article, the liberated hydrogen triggered the CO reading because the CO sensor was cross-sensitive to hydrogen. A report from the U.S. Department of Energy examining the possible generation of hydrogen and an alternate fuel source for fuel cell-powered cars reinforced this.

Regarding the basic chemical reaction, the report states, “In the vicinity of room temperature, the reaction between aluminum metal and water to form aluminum hydroxide and hydrogen is the following: 2Al + 6H2O = 2Al(OH)3 + 3H2.”¹ The result of the reaction is three hydrogen molecules. Considering the amount of sludge (and aluminum bits) in the bottom of the tank, it is very likely that this was the source of the hydrogen that activated the CO detector.

Read the Manual

Typically, CO sensors are cross sensitive to other gases such as propane; acetylene; and, as we see in many case histories, hydrogen. The gas detector is just the first step. Think of the reading as a clue. During a size-up, it takes some detective work to verify the readings and corroborate them with the actual causes and conditions—for example, on arriving at a CO call to find no symptoms and no obvious source of CO. It is important to start thinking about cross sensitivities and other factors.

A common source of false CO readings is hydrogen, driven off overcharged lead-acid batteries in vehicles, golf carts, forklifts, and even battery backup for sump pumps. Read the manual to determine what correction factor is needed to multiply the reading by to get the true amount of gas in the environment. In short, calibrating the instrument to a specific gas will provide true readings for that gas. Now it is sensing another gas that it is not calibrated—or designed—to accurately detect that is the cause of the inaccurate readings.

JERRY KNAPP is the chief of the Rockland County (NY) Hazmat Team, has a degree in fire protection, is a 48-year veteran firefighter/emergency medical technician (EMT) with the West Haverstraw (NY) Fire Department, and is a former paramedic. He served on the technical panel for the UL residential fire attack study. Knapp is the coauthor of two Fire Engineering books: House Fires and Tactical Response to Explosive Gas Emergencies. He is a contributor to Fire Engineering and several state, national, and international fire service trade journals. He is also the author of the “Fire Attack” chapter in Fire Engineering’s Handbook for Firefighter I and II. He retired from the U.S. Military Academy, West Point, where he served as the plans and operations specialist at the Directorate of Emergency Services.

JEFFREY DIMETRO is a career lieutenant with the Kingston (NY) Fire Department and assistant chief of the Highland (NY) Fire District.

Lessons Learned

As we look back on this call, we realize our gas monitor alarm should have prompted us to mask up. Because we thought the readings were unusual and there was no smell, we did not use masks. I had been on one other call last summer, where a self-heating hot pot meal had been the cause of a CO alarm activation, but the numbers on our gas monitor were not high. With the right-sized space, the right amount of hydrogen, and an ignition source, these self-heating hot pot meals can cause an IDLH environment or become combustible. Their packaging includes warning labels that recommend using them outdoors (or in a well-ventilated area). The packaging also suggests avoiding using them in small spaces and vehicles.

This was a good reminder for my crew- including myself. When the gas monitor goes into alarm mode, trust it, step back, go on air, and treat the situation as if you’re in an IDLH environment.

MREs can also produce hydrogen as the plastic containing the heater becomes damaged and is exposed to water. MREs may be more common in other areas than they are in West Yellowstone, so it is important to be mindful and prepared.

My AAR, along with partnering with FDIC connections, resulted in several important lessons learned. Never stop learning and asking questions-this is how we become better firefighters.

ENDNOTE

1. “A Study of Issues Related to the Use of Aluminum for On-Board Vehicular Hydrogen Storage.” U.S. Department of Energy, vol. 1, 2008, bit.ly/3YLXa5h.

Author’s note: Thanks to Jerry Knapp for his help with this article.

KAYLA WILSON is a firefighter/EMT with four years of experience for Hebgen Basin (MT) Fire District, where she is the vice president of her local union. She is a member of the ISFSI. Her first introduction into the emergency medicine field was in 2015 when she received her outdoor emergency care (OEC) certificate while she was working at Snow Basin Ski Resort to become a ski patroller. It was during that time that she pursued her EMT and became interested in the fire service. Wilson aspires to study and receive a degree in fire science and further her knowledge about the fire service.