How to Test Room Pressure With a Manometer

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Bathrooms typically have a slightly negative pressure because of exhaust fans.
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The pressure of a room and the overall pressure of your home affects the quality of the air. Measuring the pressure with a manometer can also pinpoint trouble areas, such as drafts. An overly positive pressure indicates that the inside air is being forced outside. Rooms with a negative pressure draw in the outside air. Negatively pressurized rooms shouldn't house combustion appliances, like space heaters, furnaces and clothes dryers because carbon monoxide can build up. Check the pressure with a manometer to ensure a safe, comfortable home.


Step 1

Close all of the windows inside the room that you wish to test. Turn off any fans. Exhaust fans will affect the pressure reading.

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Step 2

Close all of the interior doors leading to the room.


Step 3

Insert the end of the hose of the manometer underneath the door. Connect the other end to the manometer.

Step 4

Press the "Baseline" button, then the "Start" button on the device.


Step 5

Wait for the number on the display to appear. If the number fluctuates, wait for it to remain constant. Press "Enter" and read results on the display.

Step 6

Turn on the exhaust fan in the room, if there is one. Repeat the pressure reading to determine the difference that the fan makes in the room's pressure. If the room lacks an exhaust fan, skip this step.


Step 7

Interpret the results. According to Contracting Business, your home should maintain a slightly positive pressure of approximately 0.02 inches per water column. If the room has a positive pressure higher than this, air conditioned or heated air will be forced out of the home. On the other hand, negative pressures indicate drafty windows and doors.

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