It's known as a silent killer and it almost took the lives of a house full of people in Clay Township.
Five ambulances had to take eight people to the hospital after possible carbon monoxide poisoning.
This all started Thursday night at about 11:45 when Clay Fire Territory got the first medical call.
A generator was to blame and firefighters say a few simple precautions can help stop this from happening to your family.
Eight people living in a house on Gerald Street were rushed to the hospital with apparent carbon monoxide poisoning.
Gerald Gerard lives across the street and he says, "What woke me up was the flashing lights and I looked out the window and saw the street lined with emergency vehicles."
The deputy fire marshal with Clay Fire says someone from the house got home late and found another person on the floor of the home.
When firefighters got there they smelled an odor so they used a detector that showed there were dangerously high levels of carbon monoxide.
Clay Fire says there was a power outage at the house so the people were using a generator outside.
Fumes got into the house through an open window in the basement.
"In this area we've been out of electricity many times. We just bite the bullet and wait until it's back. People that use generators I sure hope they use them safely," Gerard says.
Firefighters say the best thing to do is have your generator at least 20 feet away from your house.
Plus, keep wind direction in mind when finding a place for it outside.
"Read the instructions on what it says," Ron Melser with Clay Fire says. "You never want to do it in the house. You never want to run them in the house. Keep it at a safe distance. Make sure you don't overload it."
He recommends having a carbon monoxide detector on every floor and close to any bedrooms.
Firefighters say a lot of the carbon monoxide calls they respond to happen in the winter but when it does happen this time of year it's usually during a power outage and because of a generator.
The Deputy Fire Marshal didn't know if the house had carbon monoxide detectors but he says they weren't going off so either there weren't any or they weren't working.
Gerard says he spoke to one of the people from the house after he returned from the hospital.
The man told him he thought all of the other people would be okay.