Las Vegas, NV – Firefighters rescued four people today who were overcome by carbon monoxide gas from a charcoal grill used to cook inside a house, according to Las Vegas Fire & Rescue officials.

Fire department dispatchers received a call about 2:15 a.m. that someone was sick in a home near Vegas Drive and Decatur Boulevard.

Firefighters found one person in the living room and three others in bedrooms of the single-story house, officials said. The two adults and two teens, who were semiconscious, were given oxygen and taken to the hospital, officials said.

Air monitoring equipment detected life-threatening levels of poisonous carbon monoxide gas in the home, officials said.

The occupants told firefighters they had been using a charcoal grill in the living room for cooking about 7 p.m. Wednesday, and during the night, they all started to feel sick and had headaches.

“Cooking indoors with outside cooking devices is a deadly combination,” fire department spokesman Tim Szymanski said in a news release. “Not only is it an extreme fire hazard, it also produces a deadly gas.”

Sometimes called the “silent killer,” carbon monoxide, which is odorless and invisible, can only be detected with monitoring equipment, such as a home alarm. “All homes should have a carbon monoxide alarm, one for each level of the house,” Szymanski said.

The use of outdoor cooking devices inside homes is not uncommon in Las Vegas, Szymanski said.

“Many cultures in other parts of the world cook in the living room, a place where the family gathers. With the highly diverse population here in Las Vegas, many people cook the way they are accustomed to,” he said. “Outside cooking devices should never be used inside a home.”