Your furnace filter has one main purpose and that is to prevent airborne particles from passing through your furnace and into the air you breath in your home. If your filter is built well it will achieve its goals and remove a large percentage of particles such as bacteria, mildew, pet dander and more from the air.
There are many different types of furnace filters. Each one is built for the similar purpose of filtering particles but some are able to only trap larger particles while others can trap much smaller particles. Logically, the filters that can trap smaller particles have smaller holes and get clogged much faster. For this reason it is vital that you keep your filter clean by checking it frequently. This will prevent your furnace from having to work extra hard to push air through a clogged up filter.
However, it can be very impractical to have to check your home furnace air filters so often. It is therefore mandatory that a filter finds an equilibrium between the amount it can filter and the work the furnace has to do to push air through. The furnace shouldn’t have to be over worked to produce good filtration. Many people resort to the cheap disposable variety of furnace filters but these don’t do a good job at filtering the air and they need to be changed quite often.
Pleated furnace air filters are a good choice due to their large surface area. The larger area allows them to filter more particles while not clogging up as quickly as smaller filters.
If you want to get an idea of the effectiveness of a filter you are looking at purchasing, its MERV rating will alert you to this. The higher the MERV rating, the more effective the furnace filter will be. Look for filters with a MERV rating of between 5-12. The highest numbers are often an overkill for a standard home and are really meant for health facilities such as hospitals or nursing homes.