At 12:40 this afternoon, Fairfield Engines 2, 3, 4, 5, Ladder 2, Rescue 1, and Car 3 were dispatched to a report of a strong odor of smoke with possibly visible smoke inside Planet Fitness on Black Rock Turnpike. Engine 1, on a medical at the time, quickly cleared and replaced Engine 5 as the 4th due engine. On arrival, Engine 2 went inside while Ladder 2 took the roof. Companies encountered a light odor inside but no sign of smoke or fire. Car 3 placed recall of alarm, holding Engines 2 and 4 with Ladder 2, Rescue 1 and themselves and continued the investigation. After investigating for around a half-hour, companies did not find any danger and traced the source to an issue with an HVAC unit on the roof. All units cleared shortly after and the building was able to be re-occupied.