Unmaintained machinery is more prone to break down during the peak of the season when the equipment is generally under the most stress. Regular maintenance decreases the likelihood of inconvenient breakdowns in the middle of the season and reduces future repair costs. If the ducts are not adequately maintained, carbon monoxide, bacteria, viruses, allergens, and mold can be sucked into the air you and your family breathe. If the electrical connections are poor, the wiring is damaged, or there are leaks in the gas supply lines, there is a substantial risk of fire.