Boise Fire Chief Dennis Doan said CO is clear, and odorless, but can kill if exposed to too much in a closed space. The chief also notes that a Carbon Monoxide detector is the only way to know if you're in danger.
Doan said the recent tragedy is a sad reminder of how quickly things can turn.
"That's why it makes my heart hurt; is that is is preventable and if we just maintenance our gas fired equipment and we have a CO detector these tragedies won't happen."
Most of the danger from carbon monoxide in a home is from leaky appliances which run off gas. Newer appliances can also be trouble if they don't vent correctly.
The four people who died in Pocatello had a water heater that wasn't working correctly.
Fire fighters said not only should people do regular maintenance on their appliances, but should have at least one carbon monoxide detector in the home.