Indoor air quality has a big impact on those with allergies and asthma. Since indoor air can be up to five times more polluted than outdoor air, according to the Environmental Protection Agency (EPA), taking steps to keep indoor air clean is imperative.

One of the first things recommended by allergists prescribing an allergen avoidance regimen is an air purifier. Air purifiers directly tackle the problem of indoor air polluted by a host of irritants, including dust mite allergen, mold spores, pollen, pet dander, VOCs, smoke, and other toxic fumes.

Whole house air purifiers can address the issue of polluted indoor air on a whole-house as opposed to a room-by-room basis. The idea is extremely appealing because air doesn't stay only in one room, but it flows throughout the entire house.

While whole house air purifiers have been around for a while, it's important to note that not all of them are effective. In fact, some can even produce dangerous by-products. As always, it's important to be as educated as possible when it comes to your family's health. Below is a general introduction to whole house air purification.

HOW DO WHOLE HOUSE AIR PURIFIERS WORK?

Whole house air purifiers are integrated with your home's heating and cooling system. Using the same system to control both your home's temperature and the quality of its air makes perfect sense. While your air is being heated or cooled, it can also be forced through a filter system that cleanses the air of allergens and other harmful particles or fumes (depending on the type of filters in the unit).

However, although whole house units sound great in theory, there are several factors to consider in order to make sure your choice of a whole house air purifying unit is a good one. We outline these below.

WHOLE HOUSE AIR PURIFIER ADVANTAGES

When an efficient, effective, safe unit is selected, whole house air purifiers:

• Offer air purification without "boundaries" - they clean the air in your entire home.
• Eliminate the need for multiple air purifiers around the house.
• Provide air purification without taking up space in the living area of the house.
• Provide air purification with little to no extra noise.
• Offer the benefits of clean air without the effort of having to camouflage unsightly units.
• Supply your entire family with clean air everywhere in the house, all the time.
• Save you the expense of having to purchase both air purifier filters and HVAC filters.

WHAT KIND OF FILTERS DO WHOLE HOUSE AIR PURIFIERS USE?

When it comes to whole house air purifiers, several different types of filters come into play. Many times units feature a combination of filters. Note that some of these filter types can produce undesirable by-products, such as ozone (see the section below called "Concerns About Whole House Air Purifiers").

• Media filters capture larger particles.
• Electrostatic filters use charged particles to capture smaller particles.
• Electronic filters operate on the same principle as electrostatic filters, but feature a mesh of wires that produces a constant electrostatic field. These can capture the smallest particles.
• UV filters use ultraviolet light to destroy bacteria and mold.

CONCERNS ABOUT WHOLE HOUSE AIR PURIFIERS

Concerns about whole house air purifiers fall into two categories: safety and effectiveness.

Ozone by-product being released into the home is the main safety concern when it comes to whole house air filtration. This is specifically of concern when it comes to electronic filters. As the Asthma and Allergy Foundation of America puts it:

"Electronic filters (ion-type cleaners, for example) use electrical charges to attract and deposit allergens and irritants. If the device contains collecting plates, the particles are captured within the system. The ion-chargers in these types of filters produce ozone byproduct, more than fans in mechanical filters but may still be within the acceptable level. Make sure to ask for proof from the manufacturer that their product is within the acceptable level of ozone byproduct."

In addition to the possibility of ozone being released due to the use of electronic filters, ozone may also be produced as a byproduct of UV sterilization systems.

The primary concern regarding the effectiveness of whole house air purification is the question of whether enough "dirty" air actually gets pulled into the system to provide effective air cleaning. When you choose a whole house unit, be sure to understand how it works so you can be certain of its effectiveness.

COMPARING WHOLE HOUSE AIR PURIFIERS

To be able to compare the performance of whole house air purifiers, you must understand the measurements used to calculate their effectiveness, in this case CADR and MERV.

CADR, or clean air delivery rate, was developed by the Association of Home Appliance Manufacturers (AHAM) and is the "measure of a portable air cleaner's delivery of contaminant-free air, expressed in cubic feet per minute," according to the EPA.

MERV is a rating system developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) specifically for filters. MERV stands for minimum efficiency reporting value, and it rates the filter's efficiency at removing small particles from the air that passes through it.

While you must take your home's context and the contaminants you need removed from your home's air into consideration when choosing a specific unit, CADR and MERV ratings are useful in comparing air purification systems and air filters to one another.