A backdraft is sometimes created when you run your central air conditioner with other appliances, creating a negative draft of air. This backdraft is due to a lack of proper ventilation.
A few simple solutions will temporarily stop the problem, but ultimately additional ventilation will need to be installed to permanently fix the problem.
Step 1: Open Doors and Windows
While running multiple appliances operating on the ventilation system, open doors and windows. This provides an escape route for some of the pressure and helps reduce the negative build up that occurs when the central air conditioner is on.
Step 2: Do Not Run Multiple Appliances
When running the central air conditioner, avoid running multiple appliances such as the dryer, washer and others that draw on the ventilation system and can create the negative pressure. Run the central air long enough to cool the house, then shut the system down until after you have completed the other tasks that you need to accomplish, such as washing and drying clothes.
Step 3: Contact a Heating and Ventilation Company
Call a local heating and ventilation company to come and install additional vents in the home. This will help permanently address the problem by creating additional escape routes for the pressure and releasing the build up without causing a backdraft into the chimney.