The Knoxville fire department said investigators responded to a medical call in the 1200 block of Moody Avenue on November 13 around 11:30 p.m. Upon arrival, crews said they found two male victims dead inside a duplex.

Kerosene heaters are common around East Tennessee, along with other alternative heating sources. KFD said they need to be properly ventilated outdoors.

Your car exhaust, appliances, and anything that creates a fume can give off CO.

The fire department said carbon monoxide levels were over 200 ppm inside that South Knoxville home Wednesday night.

According to the Occupational Safety & Health Administration (OSHA), 50 ppm is the maximum allowable concentration for continuous exposure for healthy adults in any eight-hour period.  A greater concentration such as 200 ppm can cause death within four to six hours of exposure.

Each year, more than 400 Americans die from unintentional CO poisoning not linked to fires, more than 20,000 visit the emergency room, and more than 4,000 are hospitalized.

The department said the best way to detect CO is with a carbon monoxide detector. You can purchase one at your local hardware store.