At ~2:50 PM, Westmoreland 911 dispatched Station 20 (Murrysville VFC) to assist Stations 87 (Harrison City VFC) and Station 63 (Claridge VFC) for a report of an odor of natural gas on Wedgewood Drive, Penn Township. Station 20 responded with Truck 20 (4 firefighters including Assistant Chief 20) which was on a nearby training exercise, and 5 firefighters on station standby with Engine 20. After surveying the area, the responding fire units found no evidence of natural gas in area, and it was determined that a mercaptan release at the nearby landfill was the probable cause of the odor within the neighborhood. Command 63 returned all responding units including Truck 20 returned to service and station.