Worst Case Depressurization Test
If you have any combustion equipment in the house - a gas or oil heater, a wood stove or fireplace, or a gas water heater, stove, or clothes dryer - you should have your house tested to see if it is likely to become depressurized enough to backdraft any of these appliances. A worst-case depressurization test involves turning on all the home's exhaust fans, the heating system, and any other appliance that pulls air from the house, and then testing the pressure in the rooms that contain combustion equipment. If these rooms are significantly depressurized, there is a danger of backdrafting. This test is usually done by a heating/air conditioning contractor.
There are many ways to solve this problem. Perhaps you only need to have your return ducts sealed. If you're purchasing new combustion equipment, consider getting a sealed-combustion or a power-vented unit. You can also add vents for combustion air from the outside into the room that contains the equipment. You may need a balanced ventilation system if the depressurization is caused by ventilation exhaust fans.