With two incidents in the last 24 hours in Philadelphia, there is important information to help keep you from becoming a victim.
"If your alarm goes off, you want to make sure you get out immediately and call 9-1-1," says Deputy Fire Chief Derrick Sawyer.
"The important thing is to have a carbon monoxide alarm in the home.
A 7-year-old boy and two adults were overcome by fumes early Tuesday morning in the Logan section of Philadelphia. The home did not have a carbon monoxide alarm.
"A person that's exposed to carbon monoxide, if they are sleeping, it is a good possibility they won't wake up," says Deputy Chief Sawyer.
Fortunately, the people in the home on the 4900 block of North Warnock Street called for help when all three of them became ill.
"You have vomiting, you have headaches, nausea," explains Deputy Chief Sawyer.
The boy has been released from the hospital, but the two adults remain in stable condition.
Deputy Fire Chief Derrick Sawyer says it could have been much worse.
"It will kill you," he said.
There was another incident of carbon monoxide poisoning yesterday at a home on Weymouth Street in Juniata.
Neighbors says a man who lives there was stricken by the invisible, odorless gas, but has since recovered.
The home does have a carbon monoxide detector.
As a precaution the fire department also checked adjoining homes to ensure no fumes entered them from next door.
"They went in the basement and checked everything, and then they went upstairs in the hallway and checked everything up there, and everything is okay," said Nassir Bsharat.
Major sources of carbon monoxide in homes are fuel-burning heaters, not electric heaters, water heaters, clothing dryers and fireplaces.
"If you don't make sure those things are properly maintained and cleaned, what can happen is carbon monoxide can back into your home," said Chief Sawyer.
And Chief Sawyer says never leave your vehicle running in a closed or opened attached garage.
"Even if it is open, you have some air those CO fumes can seep into your home," Chief Sawyer said.
He says the most important thing to remember is to have a carbon monoxide detector in your home and test it monthly.