Ventilation System Maintenance
From bathroom and kitchen exhaust fans to house air exchangers, the most important tip for ventilation systems is to keep them as clean as possible. Periodically remove the covers from bathroom exhaust fans, and vacuum the accumulated dust from inside the fan housing. A damp cloth will help clean the fan blades.
For kitchen exhaust fans, you should be able to remove the filter (usually by unclipping it and sliding it away from the fan housing) that collects cooking grease. Clean it by immersing it in hot water with a grease-cutting dish detergent added. Clean the fan blades with a cloth soaked in the same solution. If the filter is starting to deteriorate, replace it with a new one. Similarly, if your fan unit has two filters (a metal one for grease and a charcoal one for odors), the charcoal filter will have to be replaced periodically, as it can't be cleaned.
For air exchangers, first shut off the power supply to the exchanger. Open the cover that protects the filter, and remove and clean the filter (for the filter location, check your owner's manual). Replace the filter and cover, and restore the power supply.