Operate and maintain furnaces, auxiliaries, and other equipment in the buildings, replace air filters, continually check all mechanical devices and controls to assure continuous heat, hot water service, pool operation, and air conditioning, to make certain all equipment is operating safely and efficiently. Maintain an ongoing preventative maintenance program on all hot water heaters, appliances, sewer lines, lighting, furnaces, air conditioners, electrical fixtures, and roof, asphalt, and building structures.