An emergency for a heating system is any situation that puts the health, safety, or comfort of the building occupants at risk. This may include a complete system breakdown in cold weather, loss of heat due to a gas leak or power outage, carbon monoxide or gas leaks, malfunctioning controls or thermostats, and more. Any situation that poses a risk of fire, explosion, or exposure to toxic fumes or extreme cold temperatures should be considered an emergency and addressed immediately by a licensed HVAC professional.