Air Filters

An air filtering system (also called an air cleaner or air purifier) is a device that removes airborne particles by moving air through a filter. There are several styles and types of filtering systems commonly available for household use.

Household units are either part of the heating and cooling system or are portable and used in specific rooms. The most common types of filters in these systems are carbon, HEPA, fiber or electronic. Each system has advantages and disadvantages, so it is important to be informed before purchasing.

Why Use An Air Filtering System?

We are all affected by what we breathe. The cleaner the air around us is, the better we will feel and the less prone we may be to common respiratory ailments.

Air naturally has particles of dust and debris in it. While most of these particles are safe, some may be contaminated or come from an unhealthy source. Examples of airborne contaminates include: dust mites, allergens such as pollen, mold and mildew spores, and toxins from second hand smoke.

The need for an air filtering system becomes even more important as homes become more efficient. Energy efficient homes are reasonably air tight, which slows the rate of air exchange inside. The EPA suggests this lack of frequent air exchange can allow contaminates inside a home to build to 2 to 5 times more than outside.

As the level of exposure to contaminates increases, so does the risk of attacks of asthma, allergies, sour throats and other infections, such as eye, ear and sinus.

An air filtering system, when properly used, can greatly improve airflow in a home and remove up to 99% of all airborne particles.

What Is HEPA And Is It The Best?

HEPA stands for High Efficiency Particulate Air filters. HEPA filters were originally designed for use in laboratories, where any dust or contaminate could pose a problem.

A True HEPA filter removes 99.9% of all particles 0.3 microns or bigger, while a regular HEPA filter removes at least 90% of all particles 0.3 microns or bigger. A micron is 1 millionth of an inch. For comparison, the thickness of a human hair is about 200 microns and a single skin cell is about 10 microns.

The HEPA filter's removal of such fine particulates creates its weakest point. Air flow through the fine filter is greatly restricted, thus reducing the volume of air per hour it can clean. That makes it a poor choice for use with a heating and cooling system.

Other Factors To Consider

Several things need to be considered before purchasing an air filter. It is important to know the area that the unit will be used in, and if other sources of contamination have been controlled.

Typically a portable unit should be placed in either the most problematic or most often used room in the house. If the unit is capable of cleaning more air than is in the room (it should be able to circulate and filter the air about 10 times an hour), or as the furnace moves air through that room, it will have a trickle effect in surrounding areas.

Most people sleep about 8 hours a day, so a good location for a portable unit is in the bedroom.

An air filtering system is best thought of as a second line of defense. If there is a major source of uncontrolled contamination, it will be spread as the air filter works -- thus negating most of the benefits.

Common sources of pollutants are dirty furnace filters, mold and mildew in the bathroom and kitchen, shag carpeting, old pillows and furniture, pets, and smoking. If at all possible minimize these things before installing an air filter.

The difference in filter types reflects the application of the unit. If you are trying to reduce allergens and toxins from smoking, then a HEPA or electronic unit may be your best option, but they can be fairly noisy. If you simply wish to improve the general quality of the air in your home or need to have a quieter unit then a carbon-based unit may be suitable.

The prices of various units can be very confusing. An initially inexpensive unit may have expensive filters that need to be replaced every few months. Also, for a large room it could be more cost effective to purchase two small units instead of one large unit. A simple way to compare similar units is to figure out their true cost as shown below.

True cost = unit price + (filters + electricity for 1 yr)/sq feet air cleaned.

• Unit price is the initial cost of the unit at the store.
• Filters is the cost to replace all filters for one year. Filters may not last as long as indicated on the package, so it may be fair to add 10%.
• The amount of electricity used is often displayed on the packaging. Multiply this number by current rates in your area to estimate the cost of the electricity.
• Sq. feet is the area that the unit is rated to clean.