Around 1:30PM Limerick Fire Department was dispatched for a building investigation. Employees had an odor of something burning. Engine 51 and Tower 51 responded. Engine 51 staged to the front of the building while Tower 51 was ordered to the rear of the building. Fire crews found HAVC technicians on location who were working on rooftop units. Crews assessed the heater and found some insulation that had burnt.