The basic function of a furnace filter is to filter the air that passes through your furnace and into your home. The filter is meant to remove particles that can both harm your furnace and can harm your family members. These particles include such things as dust, pet hair, mold and plant spores.
Furnace Filters come in a variety of types. Although they all do the work of filtering the air, they can have larger or smaller holes and thus trap larger or smaller particles. Filters that trap smaller particles get clogged quite quickly so it is important to check and clean those filters frequently to prevent an unnecessary strain on the motor of your furnace.
The problem is that you may not always remember to check your filter and it is impractical to assume that people will do so. For this reason, a furnace filter needs to have the right filtration while at the same time not stressing your furnace by forcing it to work harder to push air through very small holes that have the tendency to get clogged. Many people use disposable filters since they are cheap but they are not effective at filtering very small particles and are meant more to protect your furnace from large particles rather then filter the air in your home.
A better choice is the pleated furnace air filter. These have a much larger surface area which means that they can catch more particles and they don’t get clogged up so quickly.
When shopping for furnace filters look for the MERV rating. This is a measurement which shows you how good a filter is at filtering particles. The higher MERV rating the more effective the filter will be. Acceptable rates range from 5 – 12. The higher ratings are really only necessary in hospitals.