Having said that, the obvious exception is when cigarette, pipe or cigar smoking occurs on a regular basis. Now the pollution can’t be missed, you can see it and you can smell it. The health concerns regarding smoking are well known and possibly beaten to death, so we won’t get in to that. Not so obvious is the health impact of dirty interior air when we don’t notice it. Medical experts have concluded that symptoms ranging from headaches, asthma, bronchitis, allergies and cancer among others, may likely be attributed to polluted interior air.

The next reason to use a furnace filter or air conditioning filter is to keep your heating and cooling system operating as it was designed and to prolong its life. For an air conditioning unit to operate at its peak efficiency it needs to be kept clean. The evaporator is the component in your system in which the air passes directly over and is cooled and returned to your living space. The surfaces of the evaporator are normally very cold and therefore wet with condensation. The moisture in the air condensates on the evaporator and subsequently drains to the exterior of the building. Imagine blowing dirty air across the cold wet surfaces of the evaporator. How long do you think it takes for the dirt to completely cover this wet surface? Once dirty, the evaporator loses efficiency and may begin to support mold and bacteria growth, after all it is a dark moist environment.

The last reason for using an air conditioning filter and furnace filter is to help keep your house clean. Look at it this way, every time your air conditioner or furnace runs it is like someone is vacuuming the air of dust, dirt or worse. All of this for only a couple bucks per month, seems like an obvious choice, your air must be filtered. What may not be obvious is which furnace filter and air conditioning filters should be used, we will try to help with that decision.

Smoke will remain suspended in the air while the others will settle after a time. Specialized air cleaners are available and for some people these will provide a real benefit. For most people the filtration products available to work with your central air system are sufficient.

In order to clean the air effectively and allow the air conditioning system to operate efficiently and as it was designed, the following criteria should be considered:

- The air filter should be easy to change or clean or should be of a self cleaning type.
- The air filter should have the capacity to trap and hold a large amount of contaminant without adding too much resistance to the air flow.
- The air filter should be efficient in trapping and holding dust, fumes, pollen, bacteria and smoke which are present in most interior environments.
- The air filter should be able to operate effectively and efficiently with various equipment which may have varying air velocity characteristics.
- The air filter should leave the filtered air clean from contaminants including those which are added in the manufacturing process to improve performance.

This may seem to be an intimidating list of requirements but there are many products commonly available which will meet or exceed these requirements. Unfortunately, there are just as many or more which do not meet the requirements. A visit to your local retailer will likely provide a wide range of available products form those which are very suitable to those that are almost useless.

The information contained in this site should provide you with enough valuable information to make the selection of the right air conditioning filters much easier.

One factor to consider is air flow through the system. Air conditioning systems are designed to operate most efficiently with the airflow remaining within the designed range. More air flow is not good but is difficult to achieve but low air flow is not good either and is quite easy to achieve. Leaving a dirty air filter in place may result in low air flow and possibly cause the system to malfunction. In some cases, using an air conditioning filter that is too restrictive for your system may cause low air flow problems as well.

In the old days the filters were commonly the fiberglass variety which might equal a MERV 1 or 2. These provide very good flow but not much filtration beyond the sizable particles in the air. They will help to prevent the evaporator from getting too dirty too fast but they don’t do much to improve air quality. On the other end of the spectrum are the MERV 15 or 16 filters which do an excellent job cleaning the air but are too restrictive for most home systems.

If you are wondering what MERV to try keep these recommendations in mind;
 -ASHRAE recommends MERV 6 or higher
 -US Department of Energy recommends MERV 13
 -Leadership in Energy and Environmental Design, LEED recommends MERV 8 at a minimum

Keep the air flow issue in mind and if possible start with a MERV 6 and work up if no system  performance problems are noted. Most importantly, change you air conditioning filters regularly according to the manufacturer’s recommendation.