In its publication “Guide to Air Cleaners in the Home”, the US Environmental Protection Agency (EPA) says, “Indoor air pollution is among the top five environmental health risks.”
Pollutants harm everyone, not just those with asthma, allergies or lung disease such as COPD/emphysema.
Pollutant summary: Particles commonly found in residential air include mold, dust mites, pet dander, microplastics, pollen, bacteria and viruses. The EPA lists gaseous pollutants known as volatile organic compounds. VOCs leach from flooring and furniture, chemicals from cleaning agents and pesticides and tobacco smoke when smokers are in the household.
Did you know that these pollutants are also found in air fresheners!
Indoor air pollution is a serious concern. Is a whole-house air purifier the answer?
Here’s your research into air purifiers for central HVAC systems:
- What they are
- Residential air purifier types
- Pros and cons
- Indoor air purifier cost
- Whether they are worth the money
- What else you can do to purify the air in your home
Central Air Purifiers – Types and How They Work
These units are also called air cleaners – their purpose is to remove pollutants and allergens from the air in your home using filters.
We’ve also completed a guide in UV light air cleaners that kill bacteria and viruses in your HVAC system and the air that flows through it.
Type 1: Media Air Purifiers
Also called mechanical air cleaners, these use filters that are thicker and denser to trap smaller particles than standard furnace/air handler filters. They also last longer than standard furnace filters.
Most media air purifier filters have a MERV rating listed. This stands for the Minimum Efficiency Reporting Value. The higher the MERV rating, the better they filter air including very small particles.
HVAC air purifiers are installed in the return-air ductwork immediately before the air handler or furnace. Some filters are replaceable. Most are washable – but that’s a hassle you might not want.
These units don’t use electricity. They filter pollutants from the air that flows through them when the blower fan is running.
There are three specialty types of media air filters:
1). HEPA filters – To qualify as a high-efficiency particulate air filters (HEPA) filter, it must trap that trap any particle larger than 0.3 microns. HEPA filters have MERV ratings from 17-21.
2). Activated charcoal/carbon filters that remove odor-causing particles from the air. These filters are used in combination with the standard media filter to remove both particles and odors. Carbon molecules have tremendous surface area. Each pound of activated carbon has a surface area of +/- 100 acres for gas to pass through and be absorbed or to bond with.
This is an excellent combination for homes where odors from pets and cooking are an issue. If your home’s odors are caused by mold or mildew, filtering out the odor isn’t the solution. Locating the cause of the mold and remedying it critical to maintaining a healthy home.
3). Charged media filters are given an electrostatic charge in the factory. Small particles are attracted to the static charge like sweaters and socks cling when removed from a hot dryer. The charge is effective for a matter of months, and then the filter should be changed.
Pros of Media Air Cleaners:
The upside to media-type air purifiers is that they effectively remove more than 99.9% of pollutants and allergens from the air. They do what they are designed to do.
Secondly, the air purifier, replacement filters and installation are all affordable. See the section on costs below.
Cons of Media Air Cleaners:
First, air cleaners only remove air pollution when your blower fan is running. Depending on your climate, there might be two to six months of the year when you rarely run the HVAC system.
Most HVAC systems still allow you to turn the fan on, even if not heating or cooling your home. This will produce electricity cost, though less than a stand-alone air purifier when the entire year of utility costs is considered.
Secondly, they can only remove pollutants that pass through them. If your flooring is emitting VOCs, you’ll be breathing them until they can be filtered out by the purifier. If there’s a smoker in the home, second-hand smoke will still be an issue until it can be filtered out. If your home is too tightly built and no fresh air gets in, the air will quickly become polluted.
Next, media filters must be replaced regularly to remain effective. If not, they’ll become blocked and electrostatic filters will lose their charge.
Finally, media air filters can be so thick they make it hard for furnaces and air handlers to draw air through them. The result is an HVAC system that works harder, uses more energy and is more prone to mechanical failure.
Type 2: Media Air Purifiers with Photocatalytic Oxidation (PCO)
HVAC expert Jeanie Wong says photocatalysis is, “the oxidation of organic contaminants such as bacteria and mold using magnetic particles coated with titanium dioxide nanoparticles” to produce harmless substances like carbon dioxide and water. A PCO filter is coated with titanium dioxide that comes in contact with harmful pollutants. A UV light is shined onto the catalytic filter to create a reaction that destroys the pollutants. PCO technology is often used in combination air cleaners. For example, the Lennox PureAir S system uses a media filter, PCO filter and UV light.
Pros and cons of PCO air purifiers: On the plus side, this technology has proven effective and is used in health settings and food processing for air cleaning. A PCO combination or hybrid air cleaner is the most effective option available. The PCO filter doesn’t hinder airflow, so your HVAC system won’t work much harder. The downside to a PCO or PCO combination filter is the higher cost of the air cleaner and the electricity cost to run it.
Type 3: Electronic Air Cleaners (EACs)
Most EACs include two types of filtration. A pre-filter catches large particles. Then, the tiny particles in the air are charged with electricity. The charge attracts them to collector plates that have an opposite charge, like magnets. This effectively removes them from the air. In some cases, the electrical charge destroys the virus or bacteria.
These units are also called ionic and electrostatic air cleaners due to the electrical charge employed. The filters can be cleaned in a dishwasher as needed, but should be air dried.
Pros and Cons of Electronic Air Cleaners:
The filters in electrostatic air purifiers are washable. This is a plus because replacement cost is low since they last a year or more. This reduces waste in landfills too.
The downside is the hassle of washing the filter every few weeks to each month. The collector plates inside the air purifier must be washed regularly too, or they won’t attract the charged particles. The purifier won’t do its job at that point.
Another con is that electronic air purifiers trap only 95% to 97% of the particles flowing through them. As with mechanical air purifiers, electronic models only filter the air when the HVAC system is running.
Finally, electronic air filters have parts that can fail and require replacing. A media air cleaner does not.
Keep reading…the most important concern about EACs is next.
Electronic Air Purifiers and Ozone
We made this a separate section to bring attention to it.
Most electronic air cleaners emit ozone.
On the positive side, ozone is known to eliminate odors. Ozone contains three oxygen molecules. One of them easily detaches and combines with odor-causing organic compounds. Their chemical composition is changed to one that doesn’t have an odor.
There is a serious concern, though. The extra oxygen molecule can also combine with organic cells in your body and alter them with negative effects. The US EPA warns, “Relatively low amounts [of ozone] can cause chest pain, coughing, shortness of breath and throat irritation. Ozone may also worsen chronic respiratory diseases such as asthma and compromise the ability of the body to fight respiratory infections.”
Due to the health risks, we recommend that you avoid ozone-producing air purifiers. If the manufacturer’s literature or representative cannot positively confirm that no ozone is created, avoid that model. The risk outweighs the advantage.
Where odors are an issue, the best option is to choose an air purifier, either electronic or media-only, that uses carbon/charcoal rather than ozone to remove odors.
Combination Air Purifiers
Some whole house air cleaners combine the technologies discussed here – media filters, electronic charging and UV light. The cost goes up for these units, but they have the advantage of removing small and large particles plus odors.
HVAC Indoor Air Purifier Cost
This table summarizes the various costs for the type types of air cleaners described above.
For any of the units, the size and features are the main factors in the cost of the units.
Are Add-on Air Purifiers for HVAC Systems Worth the Money?
You might be thinking that your HVAC system already has an air filter in the furnace or air handler, so why is another filter needed?
The answer is that it might not be.
If you’re not experiencing breathing or allergy problems, adding more equipment to your HVAC system probably isn’t a cost-effective response to indoor air pollution. See the recommendations below for improving indoor air quality in any home.
For those with breathing trouble, a central air purifier can be part of a broader solution to indoor air pollutants in your home.
Here are the three types and they’re recommended uses:
- Media air cleaners: A good fit for homes with healthy inhabitants. Good for homes where less than 3 pets live. A high-MERV or HEPA filters should be used in homes in dry, dusty climates.
- Media plus PCO air cleaners: These cleaners have the same benefits as media air cleaners, but are especially useful where household odors are also a problem.
- Electronic air cleaners: Best for homeowners that don’t want the cost of replacement filters. Some studies show that electronic air filters also kill viruses and bacteria more effectively, so might be useful in homes with small children and the elderly who are susceptible to illness.
- Combination units: These advanced air purifiers use multiple means of cleaning the air. They are ideal for households where members have known breathing issues including asthma, allergies and COPD.
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The Pollution Solution for Any Home
Healthy indoor air is achieved through a range of practices. Installing an air purifier can be one of them.
Other tips are:
- Choose low-VOC flooring and furniture for your home.
- Use natural cleaners instead of those high in chemicals.
- Tighten caps on all paint, cleaners, pesticides and other chemical-heavy products or store them away from living areas.
- Dust and vacuum weekly using a HEPA-filter vacuum.
- Change or wash all air filters as needed.
- Open windows for a period of time each day to allow the exchange of polluted indoor air for fresh outdoor air.
- If open windows increase allergy concerns, run central air conditioning to filter the air.
- If you want more consistent air exchange, consider an energy recovery ventilator (ERV) in moderate and warm climates or a heat recovery ventilator (HRV) in cool/cold climates.
- Do not smoke indoors.
- Use a vent hood over the stove when frying foods.