A six-story apartment building at 343 South and 500 East in Salt Lake City was evacuated after firefighters found an increased level of carbon monoxide inside.

A resident called in about the smell of smoke about noon, but when crews arrived they found a worker outside overcome by carbon monoxide and high levels of the gas inside, said Salt Lake City Fire Department spokesman Mark Bednarik. That worker, a man in his 40s, was taken to a hospital in serious condition.

The man was using a gas-powered concrete-cutting saw on the first floor in an office area.

"I believe it might have just been him," Bednarik said.

The fumes dispersed through the building's ventilation system, he said. No other medical problems were reported.

Nearly 40 firefighters and support personnel went to the scene. They went door to door and checked every apartment to make sure no one else had been overcome, Bednarik said. Crews used fans to clear the gas from the building before letting residents back inside.