08/22/2026
Rockerville personnel found a terrible smell at our St. 2 yesterday. This smell was definitely not propane, which is our fuel source for that station. After pulling out one of our CO monitors that we recently purchased late last year to respond to CO gas calls, the monitor alarmed with unhealthy levels of CO gas as soon as it got through the door. At this point Rapid City Fire Hazmat was requested to assist us. In the mean time we left the station closed, and turned off the power, backup generator, and propane to the building.
Upon arrival of Hazmat 6, RK personnel explained that the odor had begun sometime around Wednesday morning, approximately 24-30 hours prior. (At that time it was just a light odor and didn't permeate through the building. We were not able to find any sewer issues, and we don't store any major chemicals at the station.) Hazmat fired up their multiple sensors and entered the building. They reported high levels of hydrogen cyanide as well as carbon monoxide. These levels increased the deeper they got into the building (personnel were utilizing SCBAs due to the unhealthy environment). After searching the areas of highest concentration, nothing obvious was found. Given there were no explosive levels of gasses found by Hazmat, we opened all overhead doors to clear out the building.
We had checked the floor drains, showers, etc. to make sure there was no sewer problem. One of the Hazmat techs mentioned a battery. So we popped the hood to our Type 6 wildland engine closest to the highest readings. Sure enough, the 12V vehicle battery was hissing, warm, and bulging. We immediately unplugged the battery from the shore charger. The battery was removed and was replaced with a new one. This battery was about 7 years old, but had not given us any signs of issue. We had even been using that truck on the most recent wildland fires.
This was an unusual situation for us that we wanted to share, since we know many in our community plug their campers or vehicles in to keep the batteries charged. In a relatively short amount of time, the offgassing of the battery provided an unhealthy environment at our fire station. Thankfully we detected the severity of the issue and brought in the experts to help us solve the problem before anyone got sick.
If something doesn't smell right, get it checked out. This odor was very pungent and we knew something wasn't right. Thanks to donations received, RKVFD purchased small portable CO monitors last year to help us identify these situations. The irony is that this was the first time our CO monitors were utilized, but they worked and did their job. Thank you to Rapid City Hazmat for their assistance on this incident!
UPDATE: Thank you all for the great conversation! Our goal was to allow this to be a learning opportunity, and it has.
After the follow up with Hazmat, they said the "Hydrogen Cyanide sensor was most likely picking up Hydrogen gas coming from the battery. Hydrogen Cyanide should not be a byproduct of an overheating 12-volt battery, but a Lithium-Ion battery could create that gas. The Hydrogen Cyanide sensor can be cross-sensitive to the Hydrogen gas and create a false-positive." It was still an environment we did not want to be in.
