When it comes to air pollution, there’s no place like home. Today’s tighter houses keep the weather outside, but they also keep contaminants inside. According to the Environmental Protection Agency, the air indoors where we spend as much as 90 percent of our time can be more polluted than even city smog.
And dirt you can see is just the beginning. That dust collecting on end tables and bookshelves is only a fraction of what’s actually swimming around in the air: an invisible mix of dust mites, pollen, dander, mold, and smoke that can be annoying to breathe and hazardous to your health.
The first line of defense against airborne contaminants is to keep a house clean and well ventilated. But for some sensitive people that may not be enough. That’s where air filters come in.
How Do House Air Filters Work?
Household air filters are available in two basic types: media filters, which create a physical barrier that traps minute particles, and electronic filters, which use a high-voltage charge to attract and capture contaminants.
A few air filters are hybrids that combine both methods, and some include activated carbon elements to combat odor. Learn about the types of air purifiers below.
Typically, air filters are either built into the heating and cooling system (whole house filters) or are freestanding units that can be placed in individual rooms (portable filters with self-contained fans).
4 Types of Whole House Air Purifiers
Whole house filters, like the extended media filter shown here, must be professionally installed in return-air ductwork. Photo by Keller & Keller
The most efficient way to filter household air is through your home’s forced-air heating or central air-conditioning system. The filters are built into the return-air ductwork, trapping particles as air passes through.
Such systems are passive; as long as the fan is running, they are constantly filtering all the air in your house. Whole-house purifiers come in four main types.
1. Flat Filters
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If you have a forced-air furnace, you’ve already got a rudimentary air-filtration system: That matted-fiberglass filter that should be changed once a month. “You can’t change it often enough,” says This Old House plumbing and heating expert Richard Trethewey.
When it clogs with dust, it stops working and overworks the furnace. In fact, those filters are designed to protect your furnace from large particles of dust, and while they might keep surfaces in your house a bit cleaner, they won’t block the microscopic particles that are most irritating to lung tissue.
Pleated filters, which pack more material in the same amount of space, cost a few bucks more and do a slightly better job. By far the best-pleated filters are electrostatically charged to attract allergens like pollen and pet dander. They cost around $15 and should be changed every two to three months.
2. Extended Media Filters
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Picture a stack of furnace filters about 8 inches thick and you get the idea of an extended media filter. These boxy units contain an accordionlike pile of filtration media, which makes them more effective than regular fiberglass filters.
They require professional installation because the large filter holder must be plumbed into the ductwork. The price, including installation, ranges from $400 to $600; you’ll need to replace the $40-to-$60 filters every year.
3. Electronic filters
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These high-tech units, sometimes called electrostatic precipitators, are also incorporated into the ductwork. As air passes through, a high-voltage current puts an electrical charge on particles. At the other end of the unit, oppositely charged collector plates grab the particles like a magnet.
Electronic filters work especially well on smoke particles too small to be trapped in media filters. One independent test found such filters worked about 30 times as well as regular fiberglass filters. (There is no industry yardstick for measuring the effectiveness of whole house units because performance is affected by a home’s blower and ductwork.)
Unlike media filters, electronic filters never need replacing, but the aluminum collector plates must be cleaned in soapy water every few months. The process of charging particles, called ionization, may produce trace amounts of ozone, a lung irritant. Electronic filters cost $600 to $1,000 installed and require a 120-volt electrical outlet.
4. Ultraviolet Filters
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People worried primarily about germs can consider an ultraviolet filter. Typically, UV filters are built-in components, sold as add-ons to a whole-house electronic precipitator (as in, add on $400 to $800).
The ultraviolet light zaps airborne bacteria and viruses into oblivion, which is why hospitals use UV air filters in tuberculosis wards. Of course, the bug has to reach the filter before it can be zapped; if someone sneezes in your face, UV technology won’t help.
Portable Room Air Filters
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If your house has no central air-conditioning or heating, portable room air filters are the most practical choice. Freestanding whole house units exist, but they typically require attic installation and ducting to individual rooms.
Most portables employ highly effective HEPA filters, which are not generally used in whole-house systems because they need more-powerful fans than furnaces can provide.
Some portable units, called ion air cleaners, use electrostatic precipitator technology. Ion units, which don’t require fans, are typically quieter than HEPA models and cost less to operate because there are no filters to replace. But these units may produce trace amounts of the lung irritant ozone as a by-product of the ionization process
Portable units range in price from $150 to as much as $1,500, and there are ongoing costs. HEPA filters, which must be replaced annually, cost from $40 to more than $100.
Portables can also be noisy because it takes a lot of wind to push air through such a fine filter. Some manufacturers are addressing the noise issue with so-called smart filters that employ an optical sensor to judge when the air is relatively clean, then switch to a lower fan setting. Another strategy is to run a portable filter on high during the day, then turn it to low at night.
Portables powered by fans are rated by “clean-air delivery rate” (CADR), which measures both air movement and gunk-trapping effectiveness. It’s important to buy a filter that’s big enough. Manufacturers recommend that the CADR be at least two-thirds the room’s area in square feet — so a 15-by-20-foot room (300 square feet) would need a filter with a CADR rating of 200. (The calculation assumes 8-foot ceilings.)
Portable Ion Units
Portable ion units are similar to whole-house electronic filters in that they both put an electrical charge on particles.
In a whole-house system, the particles of dust and pollen are charged as they pass through the unit, then captured on an oppositely charged collector plate. Portable ion filters, which operate without fans, send streams of negative ions directly into the air.
Charged airborne particles are then attracted to a collection rod in the unit (which needs occasional cleaning), or with some models allowed to land on surfaces in the house (where dusting removes them from the room).
Pro2ProTip: Ion air filters should not be confused with ozone generators, a different type of air filter that relies on ozone to clean the air and is not recommended by the EPA or the American Lung Association.)
As a by-product of the ionization process, these types of units may produce trace amounts of ozone, a lung irritant.
Ion filters are considered safe if they release less than 50 parts per billion of ozone, the government’s threshold. But even smaller amounts could bother people with asthma or other breathing disorders.
If you’re considering a whole house or portable electronic filter, check the product specifications to make sure it does not exceed safe levels for ozone emission.
Getting Hep to HEPA
High-efficiency particulate air (HEPA) filters were invented during World War II as a way to prevent radioactive particles from escaping laboratories.
The filters are made of various synthetic fibers; there is no construction standard because the term merely designates an efficiency rating: the ability to block 99.97 percent of all particles 0.3 micron or larger.
Note: A micron is a millionth of a meter, or .000039 inch; the naked eye can’t see anything smaller than about 25 microns.
That rating is for laboratory conditions, however. Experts say that at home you can realistically expect a HEPA filter to grab about 80 percent of such particles.
A new filter technology for the home, called ULPA (ultra-low penetration air), has raised the stakes. ULPA filters block 99.99 percent of particles measuring 0.12 micron, quite a bit smaller than the HEPA threshold. But ULPA filters restrict so much airflow that in practice they are able to clean less air than HEPA filters. For best performance, look for those labeled “true HEPA.”
But Do They Really Make You Feel Better?
Air filters, in general, do a good job of clearing the air. But do they actually make you feel better? The medical verdict is still out.
According to Andrew Filderman, M.D., a pulmonary specialist in Rockport, Maine, no controlled studies have been done on the subject. “We know these things filter the stuff, but we don’t know if it helps,” he says. “It’s difficult to prove because there are so many provocative things in the air, and you don’t always know what’s causing the problem.”
Dr. Filderman adds that while some allergic or asthmatic patients report benefits from air filters, the evidence remains anecdotal. “If source control and ventilation don’t help,” he says, “it’s not unreasonable to try a filter.”
Where To Find It
Flat Furnace Filter
Fiberglass-mesh and standard pleated
Chicago, IL
877-345-3371
www.filtersUSA.com
Extended Media Filter
Model# 2200
Aprilaire
608-257-8801
www.aprilaire.com
Electronic Purifier
Enviracaire Elite F300E
Honeywell
Morristown, NJ
800-328-5111
www.honeywell.com
UV Filter
PureAir Air Purification System
Lennox
Richardson, TX
800-953-6669
www.lennox.com
Portable Air Purifiers
Blueair 501
Blueair, Inc.
Provided by Pure n Natural Systems, Inc.
Morton Grove, IL
800-237-91199
www.purenatural.com
Whispure Model# AP25030H
Whirlpool
800-253-1301
www.whirlpool.com
FAQs
4 Types of Whole House Air Filters? ›
HEPA Filters
High-efficiency particulate air (HEPA) filters are recommended by the U.S. Department of Health because they are able to remove at least 99.97% of airborne allergens and pollutants — including mold spores and dust that are as small as 0.3 microns.
HEPA Filters
High-efficiency particulate air (HEPA) filters are recommended by the U.S. Department of Health because they are able to remove at least 99.97% of airborne allergens and pollutants — including mold spores and dust that are as small as 0.3 microns.
Activated carbon filters and UV air filters remove toxic gases and microorganisms in the air respectively. HVAC air filters protect the critical components of the HVAC unit and purify the air for the users. The types of HVAC air filters are AC filters and furnace filters.
What are the 4 types of filters? ›Figure 4.8 Four common filter types (clockwise from upper left): low-pass, high-pass, band-reject, band-pass. Figure 4.8 illustrates four basic types of filters: low-pass, high-pass, band-pass, and band-reject.
Which is better for your HVAC system HEPA or MERV filters? ›MERV 13 filters are more efficient at removing large particles from the air, while HEPA filters are more efficient at removing small particles from the air. MERV 13 filters can remove up to 99.97% of particles from the air, while HEPA filters can remove up to 99.99% of particles from the air.
How many filters should an HVAC system have? ›Typically, a house will have 2 air filters in their intake vents. In some cases, there can be more or fewer depending on the square footage of the home or apartment and the number of floors that need to be supported by the central air system.
What MERV is best for home? ›In general, the best MERV rating for a home is somewhere between 8-10. These filters will capture a large portion of the airborne particles and improve indoor air quality without making your energy costs rise significantly.
What is the most common AC filter? ›What Are the Most Common Air Filter Sizes. Historically, when you've gone to your typical home supply store, you'd find between 10-20 size variants to choose from. These sizes reflect the most common sizes of return air vents that push or pull air into your HVAC system: 20 x 20 x 1.
What are the 5 types of filters? ›- Mechanical Filters.
- Absorption Filters.
- Sequestration Filters.
- Ion Exchange Filters.
- Reverse Osmosis Filters.
Air purifiers with a HEPA filter tend to be the best for filtering dust from your space. According to the EPA, HEPA filters can remove 99.97% of dust particles that measure 3 microns in diameter.
What is the primary filter in HVAC? ›
The primary filters are usually panel filters. These are there to catch the dust. They're typically made with a pleated design which increases the surface area and allows it to catch much more dust and last a bit longer than if it were just a flat sheet.
Does the type of HVAC air filter matter? ›The short answer is, no, they're not all the same. In fact, there are many different types of air filters available and choosing the right one can make a real difference in the lifespan of your HVAC system.
How do I know what air filter to use? ›Simply, you need the filter size that fits in your air return. You can typically find that size on the side of the air filter that you already have in use. This size will be the nominal size, which means it is rounded from its actual size. This is the size you click on at secondnature.com.
Are all HVAC air filters the same? ›No, HVAC air filters differ in quality and dimensions, and some have features that others don't. In most instances we advise using the filter your HVAC manufacturer recommends pairing with your system. All filters are assigned MERV ratings, which go from 1–20. MERV stands for minimum efficiency reporting value.
Are 4 filters better? ›With more surface area to trap airborne contaminants, a 4” media air filter offers a longer service life than a 1” media air filter does. 4” filters last longer because they do not become clogged as quickly. Less filter changes means less money spent, and convenience.
How many different filters are there? ›Every car has four main filters: the cabin filter, oil filter, fuel filter and air filter. The function of all these filters is to enable flows and catch impurities: the dust and contaminants in the air, the impurities in the fuel or the dirt in the motor oil.
What is the difference between a pressure filter and a gravity filter? ›Pressure filters are similar in concept to rapid gravity filters, except that they are contained in a steel pressure vessel. Perforated pipes or a steel plate with nozzles are used for collecting the filtered water and for distribution of the washwater and air scour.
Is MERV 13 too high for residential? ›MERV 13 is the highest MERV value safe for residential furnaces; the higher ratings are used primarily in commercial units. 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.
Is there a downside to high MERV filters? ›If the MERV rating on your furnace is too high, it may force your furnace to work too hard and leave it vulnerable to damages. In addition, you may not get the air velocity required to reach all parts of your home leaving inconsistencies in temperature.
What is the main drawback of using a high MERV filter? ›The higher MERV filters have higher resistance. When you add more resistance, you can get a bigger pressure drop across the filter. And that's where the problems begin. The blower in the furnace or air handler is rated for a certain amount of pressure drop.
Is MERV 8 too restrictive? ›
In many cases, a MERV 8 air filter is more than adequate. However, if you are worried about outdoor air pollution, family members with respiratory issues, pets are in the home, then going with a higher MERV rating might be a good idea.
Do more expensive HVAC filters work? ›More expensive air filters such as Pleated Residential filters will filter out dust mites, pollen, pet dander, mold, and even bacteria, which can be worth the extra money, especially for those with severe allergies.
Do I need filters in my return vents? ›Do Return Air Vents Need Filters? If your HVAC system has a filter in the air handler, return vent filters are unnecessary. Return vent filters operate behind the openings of the return vents in your house. They support HVAC system components by removing solid contaminants from the air.
Is MERV 5 OK for home? ›MERV 5-8 Filters: MERV ratings of 5 to 8 indicate a medium-quality filter that's sufficient for most homes. They trap particles as small as 3 microns, which include mold spores, animal dander, and the highly allergenic droppings of dust mites.
What MERV should I get for my furnace? ›The EPA recommends MERV ratings of 9-12 because it is the most effective at keeping your home's air clean. A filter with this rating will prevent particulates as small as 1 micron from entering your HVAC system. This rating qualifies as HEPA (high-efficiency particulate absorption) level.
Is MERV 8 or MERV 11 better? ›MERV 11 filters are more efficient than MERV 8 filters as they can capture smaller particles. They offer additional protection from pet dander, dust mites, auto-emissions, and lung-damaging dust. This is a good option for households with pets or those looking for even better air quality than the MERV 8 can provide.
How do I choose an HVAC filter? ›- Choose the Right-sized Filter. Check your furnace manual for the correct sized filter, or check the existing filter to determine dimensions. ...
- Choose the Right Type of Filter. ...
- Understand Filter MERV Ratings. ...
- How to Replace Furnace Filters. ...
- Project Shopping List.
More expensive filters like Pleated Residential filters filter out dust mites, pollen, mold and pet dander and even bacteria and so are worth the money especially for those with severe allergies. HEPA filters filter bacteria and viruses and are worth the extra money for those with respiratory conditions like emphysema.
What is the most expensive AC filter? ›HEPA Filters
Though they are the most expensive on the market, they last longer and keep your air cleaner.
Explanation: Nitrocellulose filters are the most commonly used filters.
What are the disadvantages of whole house water filter? ›
- Whole-house systems are significantly more expensive than point-of-use (POU) filters.
- Compared to POU systems, POEs are more complicated and costly to install and maintain.
- You need a licensed plumbing professional near you to fit this type of system.
- Active Low Pass Filter.
- Active High Pass Filter.
- Active Band Pass Filter.
- Active Band Stop Filter. This is also called as Band Elimination filter.
- Shark 3-in-1 Air Purifier, Heater & Fan with NanoSeal HEPA.
- IQAir Atem X.
- My Happi Air Purifier.
- Sans HEPA 13 Air Purifier.
- Galanz Personal Air Purifier.
- Levoit Core 400S Smart True HEPA Air Purifier.
- Bulex Air Purifier.
- Bissell Air Purifier.
A buildup of dust in your home is often the result of poor airflow. A combination of poor airflow and infrequent cleaning can lead dust and dust mites to settle comfortably into several areas in your home. “Dust mites live in mattresses, pillows, and upholstery,” Dr. Cajigal says.
How do I make my house less dusty? ›- Change air filters regularly and buy the good ones. ...
- Get air ducts cleaned. ...
- Use mats to keep dust out of your home. ...
- Take off your shoes when you enter your home. ...
- Minimize knickknacks. ...
- Dust regularly. ...
- Dust with microfiber cloths. ...
- Vacuum regularly.
One clever way to determine if the air filter is dirty is to do the "white sheet test." This involves hanging a clean white sheet approximately 5 inches away from one of the vents for at least one hour. If the sheet turns gray, you've got a filthy air filter. The grayer the sheet, the dirtier the filter.
Is furnace filter same as HVAC filter? ›While many people refer to air conditioning and furnace filters as if they're different, this is not the case. Your furnace and your air conditioning system use the exact same filter, so there's no need to worry about purchasing separate filters for each piece of equipment.
What MERV rating is best for airflow? ›Air filters that are MERV 13 and higher are recommended for those that prioritize air quality and may have to handle asthma, severe allergies, and other similar circumstances.
Do expensive furnace filters make a difference? ›Better quality – more expensive – filters trap more particles and can improve furnace performance.
How often should HVAC filters be changed? ›Generally, most air filter manufacturers and HVAC companies recommend changing your air filter every 90 days, or 3 months. That can change based on where your home is located (ex. dusty, dry climates), if you have any pets, and the age of your system and equipment.
Do Filtrete filters restrict airflow? ›
Most Filtrete™ Filters (those above MPR 300) have fibers with a permanent electrostatic charge. That charge lets filter media fibers capture teeny-tiny particles much more efficiently—without restricting airflow.
What kind of furnace filter should I use? ›The American Society of Heating, Refrigeration and Air Conditioner Engineers (ASHARE) recommends a MERV 6 or higher. Most people go with a MERV 8 filter. Most residential areas can remove contaminants with MERV 8 to MERV 13, while most hospitals use MERV 14 to MERV 20.
What are the types of filters available in an HVAC system? ›- HEPA Filter. HEPA filters offer the highest level of protection against a variety of airborne particles. ...
- Reusable Air Filters. Reusable are filters are washable filters that can simply be cleaned up and used again. ...
- Flat-Paneled Fiberglass Filters. ...
- Pleated Media Filter.
Cheap air filters don't last as long, are less efficient at trapping particles, and have a smaller surface area to filter. This can lead to poor indoor air quality and increased health risks.
What is the difference between types of air filters? ›Higher-rated filters have smaller openings, which is supposed to make them able to catch smaller particles in the air. A MERV 2 filter will only catch the largest particles, while a MERV 10 filter is supposed to catch very small particles like pet dander.
Is there really a difference in HVAC air filters? ›No, HVAC air filters differ in quality and dimensions, and some have features that others don't. In most instances we advise using the filter your HVAC manufacturer recommends pairing with your system. All filters are assigned MERV ratings, which go from 1–20. MERV stands for minimum efficiency reporting value.
How often should you change air filters in HVAC? ›Generally, most air filter manufacturers and HVAC companies recommend changing your air filter every 90 days, or 3 months. That can change based on where your home is located (ex. dusty, dry climates), if you have any pets, and the age of your system and equipment.
Are 4 air filters better? ›With more surface area to trap airborne contaminants, a 4” media air filter offers a longer service life than a 1” media air filter does. 4” filters last longer because they do not become clogged as quickly. Less filter changes means less money spent, and convenience.
Is it worth buying more expensive air filters? ›More expensive air filters such as Pleated Residential filters will filter out dust mites, pollen, pet dander, mold, and even bacteria, which can be worth the extra money, especially for those with severe allergies.
How do I know which air filter to buy? ›Simply, you need the filter size that fits in your air return. You can typically find that size on the side of the air filter that you already have in use. This size will be the nominal size, which means it is rounded from its actual size.