Sioux Falls Fire crews have responded to more than 30 carbon monoxide calls since January 1.
It's an issue homeowners deal with every winter as furnaces run at full tilt and vehicles warm up in the garage.
"A lot of times we'll come on scene and find out it was someone who started their car in the garage and that's why their CO detector is going off," Sioux Falls Fire Rescue Division Chief Jeff Helm said.
CO, or carbon monoxide, is the colorless, odorless and tasteless gas that not only can make you sick, but could be deadly if you're exposed to high levels. One of the most common sources is your car.
"There have been calls we've been on where people have just forgot they left their car in the garage. If you leave that running 15, 20, 30 minutes, even an hour, it can cause a big issue because it's going to fill up your garage with CO and it's going to make its way into the home and cause some real issues," Helm said.
KELOLAND News asked Sioux Falls Fire Rescue to stop by a typical home to test the air and see just how high the carbon monoxide levels can get inside a garage while a car is running.
The levels were consistently at zero with the garage door open even after ten minutes with the car running. But when the garage door was shut, it was a different story.
"You can tell it's starting to percolate around," Helm said.
After about five minutes, the carbon monoxide monitor started getting consistent readings.
"We're spreading it around now. We're up to 12 parts per million regardless of where I'm standing," Helm explained as he looked at the carbon monoxide monitor.
After ten minutes with the door closed, the alarm started sounding with the meter reading around 35 parts per million, which is the maximum level OSHA will allow someone to be exposed to carbon monoxide for eight hours.
"Our meter is telling us we're catching a level there that we're going to take action whether we're going to make sure we ventilate and we're going to find out exactly where that carbon monoxide is coming from," Helm said.
We wanted to see just how high the levels would climb so we had a firefighter suit up and stay inside for five more minutes. Through the window, our camera caught levels as high as 67 parts per million but the readings were much higher in other areas of the garage. The meter picked up a reading of 118 parts per million right behind the car after just 15 minutes with the door closed.
"That's getting pretty high. At 120, you'd start being sick in the next hour and stuff would start showing up with the headaches and the nausea and ringing of the ears, different signs and symptoms," Sioux Falls Fire Rescue Captain Dan Schneider said.
Once the garage door was opened, the levels dropped back down to zero within a few minutes but Captain Schneider also went inside the house to test the levels.
"We did have a little trace, a one, that came on there for just a moment," Schneider said.
Schneider says depending on the conditions outside and the seal on your door, carbon monoxide from the garage can leak into your home.
"The wind is actually blowing away from the garage door. If we'd had an east wind, it would have blown it in and we would have had a lot of carbon monoxide in here, but just remember the wind can actually force it into your house and have increased concentrations," Schneider said.
Sioux Falls Fire Rescue officials say the simplest and safest advice for warming your car up is to put it in reverse when you rev it up.
"We really discourage people from having cars in here. There's two-fold. One of them is that you have the carbon monoxide exposure issue and the other thing is we have a couple car fires every year from people who warm up their cars in the garage and they burn so it's really best to have them backed outside when they pose the least risk," Schneider said.
It's advice that will keep you warm and safe this winter from this hazard in your home.