An air filter provides a way of removing dirt and other contaminants from the air in the home. Typically this is done with a filtering appliance that captures these particles as the air moves through it, or used as part of a whole-home air system. There are many different kinds of filters, with a wide range of effectiveness and cost. Choosing the best one is a matter of deciding which one will do what you need in a way that works for your situation by comparing the efficiency and usability of various filters.
One concern when buying an air filter system is the amount of noise it makes during normal operation. Many people object to the interference caused by a noisy appliance, which can sometimes be so loud that it disrupts normal activities such as quiet conversation or watching television. Listen to the system running at both low and high speeds to see if it is going to be too noisy for the location in which you are planning on using it. If you can’t view the machine in person, read customer reviews and pay particular attention to comments about how loud it is.
An important part of any air filter is how well it does its job. Freestanding units are made to be placed in the room where they are needed and will usually only filter that air, without affecting the rest of the house. These portable systems are rated by the clean air delivery rate (CADR), which allows various units to be compared. The higher the CADR number, the more effectively the room air is cleaned. Most of these units have air filters that need to be replaced periodically.
One concern about portable air filter systems that use electronic filtration methods is the possible production of ozone as a by-product. According to the US Environmental Protection Agency (EPA), ozone can cause lung irritation, and consumers should avoid air cleaning systems that fall into this category. If you want to buy a non-irritating system, the Association of Home Appliance Manufacturers (AHAM) rates units manufactured in multiple countries, so check to make sure any air filter you are considering has been rated and approved before buying it.
Another type of air filter is not a stand-alone filter, but is one that typically fits into your home’s heating or cooling system. These can be either disposable or reusable, and are generally rated with a number called the Minimum Efficiency Reporting Value (MERV), an indicator of how many particles the filter can remove. For a home system the MERV number is usually 1 through 20, with the higher numbers representing more efficient filtering of the air. If you have allergy issues or other breathing concerns, the best filter for you will have a MERV rating of 15 or above. Make sure your system can handle the filter you choose, as some do not have the power to user the higher-rated filters and you may need to choose an 11 or 12 filter instead.