A central air conditioning system might develop unusual odors that drift into the home through the vents. Sometimes this is temporary, and the system does not require repair or maintenance. In other cases, the household residents should call for service by a heating and cooling contractor.
Even a slight odor that smells like something burning is disconcerting. It might remind a person of smoke or a tidbit of food scorching on a hot stove burner. This smell could be more noticeable near the indoor part of the equipment.
With heating and cooling equipment, this odor often occurs when someone turns on the furnace for the first time after several months of no use. However, that does not explain why the smell happens while the air conditioner is running.
If the home was smoky for any reason while the system was last used, smoke may have reached the air filter through the return registers. This could be from cigarettes, leaves burning in the backyard, or bacon frying on the stove. Changing the filter might solve the problem.
This smell could be connected with the fan motor overheating. Overheating can happen if the capacitor malfunctions or the bearings have worn out.
Odors of dust coming from the vents indicate the furnace or ducts should be cleaned. Since the furnace and central air conditioner run on the same equipment indoors, a dirty furnace has negative effects on air quality. This issue is more likely if the homeowners have not scheduled annual maintenance and cleaning for a few years.
Some households call for service because the central air system is emitting an odor that smells something like mildew or sweaty socks. A brief episode of this can be normal after turning on the machine for the first time in several months. If it continues, though, the smell indicates mildew growing in the equipment
A heating and cooling contractor can locate the source and eliminate it. Frequently, the problem is a clogged drain hose that prevents water produced during dehumidification from draining away effectively.
The household residents will likely feel alarmed if they smell odors of rotting meat coming through the vents even whether or not the fan is running. Turning the air conditioner on significantly worsens the odor. It's possible for a bird, mouse, or chipmunk to get into the equipment and die. A technician determines where the dead animal is and removes it. The odor should quickly disappear after the system runs for a couple of minutes.
Contact a local HVAC technician to learn more about air conditioning issues.