Basement Air Pressure

For buildings that have a door separating the basement from upper rooms.

A negative air pressure (partial vacuum) in the basement can do the following:

• Pull water vapor and deadly radon gas in through cracks and pores in the basement walls and floor.
• Pull air down through chimneys, preventing carbon monoxide from furnace and water heater to be safely exhausted.
• Pull sewer gasses indoors whenever the water trap in sewer drains has evaporated.

Using the central air circulation blower to make basement air pressure slightly greater than the upstairs air pressure

Adjustment of air pressure should be done when the wind is calm because in typical buildings the wind pressurizes some rooms and depressurizes others.

During the following procedure, it is assumed that the air pressure sensor is located on the basement side of the basement door.

1. Turn-on the air circulation system's blower.
2. Close the door to the basement.
3. Connect one end of the plastic hose to the pressure sensor's outlet port.
4. Extend the other end of the plastic hose under the basement door or up through a hole to access air pressure in a room above the basement.
5. Make the face of the pressure sensor vertical so that only 0.5 Pascals (.002 inches of water column) of air pressure will be required to inflate the balloon.
6. Check for movement of the balloon as shown below.
    

7.  When the reflection of the colored disk disappears, then air pressure in the basement is greater than the air pressure on the first floor by at least 0.5 Pascals (.002 inches of water column).

 8. If the colored disk's reflection has not disappeared, then do one or more of the following until the reflection disappears.

• Seal air leaks in the air-return ductwork.
• Adjust, or close, some of the inlets in the air-return ductwork.
• Open outlets in the air-return ductwork.
• Use a small blower to bring fresh air into the basement from the exterior.
• Seal air-leaks between the ductwork and the exterior.

Additional Sources of Information:

• Air Pressure in an Apartment
• Indoor Air Pressure
• Suggested Air Pressure
• Renovating Your Basement for Livability

NOTE: People with allergies and asthma benefit greatly by keeping their exposure to allergy or asthma triggers low enough to prevent triggering symptoms.