Ventilation within your bathroom is an important part of the rest of your home’s ventilation system. This is because your bathroom fan helps to improve the air quality inside by extracting humidity and odors. It is good to note that unless you have your bathroom adequately ventilated any moisture which has been generated due to showering or bathing will have nowhere to go leading to a growth of mould or mildew. A good way to know if you need to think about installing or upgrading a fan is if you see your bathroom mirror steamed up from your shower, or if you see a build up of any condensation on the windows or bathroom walls.

Several causes may be contributing if your bathroom fan isn’t working properly. Bathroom fans should be replaced or serviced for inability to overcome static pressure, inadequate airflow, high leakage rates or because they are in generally poor condition. A simple test to check if your bathroom fan is working is to turn the fan on and hold a plastic bag or a piece tissue paper up to the grill. The fan should draw the plastic or tissue paper tightly against the grill, if it doesn’t you may have a problem:

• Incorrect position of fan in room.
• Duct terminates at obstruction; several times I have seen exhaust ducting terminate before it has a chance to exit the structure. In some cases siding or roofing materials have been installed over the exhaust penetration before the vent boot has been installed.
• Check if your fan is a recirculating model. If this is the case it is designed to filter out odors instead of exhausting air. If you find filters when you remove the fan grill, you have a recirculating fan.
• Check to see if the fan is connected to exhaust ducting; usually, no duct means better air flow, but in some cases the fan may be blowing directly into compressed insulation.
• Incorrect size of duct piping used to exhaust room.
• Check the grill for build-up and clean if needed or check for obstructions in the ductwork such as birds’ nests or other debris.
• Check the flapper in the exhaust vent hood or the exhaust fan itself; it could be jammed

Sometimes the problem isn’t with the exhaust fan itself, but rather other factors such as an undersized fan, improper fan selection or lack of make-up air coming into the bathroom.