Air Purifiers

There are many different types of air purifiers also called air cleaners or air filters.

The ones I will be talking about are the ones that actually do some good and filter the air in the whole house. Yes there are room air filters and they do good job at filtering the air in a small room but you need the air filtered in the whole house and not just one room.

There are different styles and many different manufacturers of whole house air filters.

Here are the two types you can buy at Home Depot:

Flat or panel air filters with a MERV of 1 to 4 are commonly used in residential furnaces and air conditioners. For the most part, such filters are used to protect the HVAC equipment from the buildup of unwanted materials on the surfaces such as fan motors and heating or cooling coils, and not for direct indoor air quality reasons. They have low efficiency on smaller airborne particles and medium efficiency on larger particles, as long as they remain airborne and pass through the filter. Some smaller particles found within a house include viruses, bacteria, some mold spores, a significant fraction of cat and dog allergens, and a small portion of dust mite allergens. These are the cheap 1" filters you buy at the hardware store for $1-$5 each. (These are the ones that Hot 'n' Cold recommends of the 1" type of filters.)

Pleated or extended surface filters - Medium efficiency filters with a MERV of 5 to 13 are reasonably efficient at removing small to large airborne particles. Filters with a MERV between 7 and 13 are likely to be nearly as effective as true HEPA filters at controlling most airborne indoor particles. Medium efficiency air filters are generally less expensive than HEPA filters, and allow quieter HVAC fan operation and higher airflow rates than HEPA filters since they have less airflow resistance. These are the more expensive 1" filters you buy at the hardware store. ***Some residential HVAC systems may not have enough fan or motor capacity to accommodate higher efficiency filters. When they start to get dirty they restrict air flow even more. (IE-These could damage your furnace and we do not recommend you use these)***

The follow types are the add on filters that we recommend if you are serious about air filtration.

Some of them attach to your furnace's return air duct and filter the air as it is sucked into the furnace by your furnace fan. These are great and filter all the air going through the furnace as long as they are maintained properly.

They come in a few different varieties -

• some are all mechanical meaning they have a traditional pleated type filter and do not require any external power. The filters are not the 1" filters that you buy at the hardware store. They are better designed to allow sufficient air flow through the furnace and are much thicker so they last generally last a lot longer. (Think of the 1" filter only 4-6 inches thick.) This type of filter is generally the cheapest but they generally do not filter down (not as efficient) as the electronic or combo units.
• The second type is a combination of the mechanical and electronic. These are the more expensive. They have mechanical filters before the collector plates and then have the some kind of electronic collector plates. They generally have the highest efficiency rating, require external power, have to change the mechanical filters and clean the collector plates.

Mechanical only filter

Combo unit. You can see the power cord for external power.

The other type of whole house filter that we have also attaches to the return air duct but is not inline with the furnace fan like the above filters (like a bypass) and requires its own fan to pass air through the filters. It has 3 mechanical filters which get it as high an efficiency rating as the combo units above. It has a pre-filter, carbon filter, and a hepa filter. The pre-filter and carbon filter are changed regularly and the hepa filter is changed every 2-5 years. So it is quite economical to maintain. It gets power from a 120v outlet to power its internal fan. The disadvantage to this one is that does not filter all the air going through furnace.

Here is the bypass filter type. You can see the three filters in the picture.

So which filter is right for you? That depends on how much you are willing to spend and the specific furnace/duct setup you have at your house. Sometimes it is only possible (practical) to install one or the other type of filter. Sometimes only a bypass is practical to install because of the room in the furnace room or the sate of the room that the furnace and ducts are in.

A high efficiency particulate air or HEPA filter is a type of high-efficiency air filter.

Back to the Indoor Air Quality Page.