SCARBOROUGH, Maine (NEWS CENTER) -- Several people at a gym in Scarborough felt the effects of elevated carbon monoxide levels.

Complaints of sickness brought firefighters to Lifestyles Fitness Center on Pleasant Hill Road at 7:20 a.m. on Sunday.

Evaluations were performed on four people at the scene. One of them was sent to Maine Medical Center for further treatment.

A test of air quality by firefighters showed carbon monoxide levels at 600 parts per million (ppm). According to the U.S. Environmental Protection Agency, the average level of carbon monoxide in a home ranges from 0.5 to 5 ppm, although it's not unusual for levels to increase to 15 ppm in the immediate area around a gas stove.

Firefighters traced the elevated carbon monoxide levels to the gym's HVAC system. The system was shut down, and the building was ventilated.

Lifestyles was closed for the day until repairs could be made.