Types of HVAC Air Filters
The cheapest type is the fiberglass filter. It allows air to flow through freely while cleaning out dust, but they do not last very long. They need to be replaced every month for most homes (i.e. especially for homes with pets).
Pleats are rigid waves in the filter that helps to increase the surface area. These types are good at balancing air flow and filtration for a longer lifespan. They are more expensive than their fiberglass counterparts but last two to three months.
These permanent filters are washable and should be cleaned monthly for the best performance. They can be very cost effective in the long run but will cost more up front.
If odor is an issue, buy a filter with activated carbon. The carbon does a great job of neutralizing odors while filtering. They should last two to three months and are usually pleated.
Disposable filters should be replaced every one to three months, depending on the type of filter, number of pets, and the level of dust in the house. Remove the old filter and throw it away. Clean the duct and edges with a vacuum. Use a paper towel and a vinegar cleaning solution to remove tough spots.
Buy a new filter that is the correct size and insert it into the air intake. Make sure it is facing the correct direction. There are little arrows on the side of the filter that will indicate the direction of air flow.