Air Purifier for Mold: What It Can and Can't Do

A little, in a narrow way. The EPA's Guide to Air Cleaners in the Home answers the question directly: no, portable air cleaners and furnace or HVAC filters don't solve mold problems, because mold is caused by a water or moisture problem in the building that allows it to grow. The same guide says they may remove some of the particles generated by mold, but the moisture problem still has to be fixed.

Think of it this way:

Table: what an air purifier does and doesn't do about mold, based on the EPA guide.

The EPA's general rule for indoor air: the most effective ways to improve your indoor air are to reduce or remove the sources of pollutants. It describes filtration as an effective supplement to source control and ventilation, not a replacement.

You'll see units marketed as a "mold removal air purifier." No air purifier removes mold from your home. Mold grows on surfaces, and the EPA says growing mold has to be physically cleaned off or cut out: it is not enough to simply kill the mold. It must also be removed, because dead mold is still allergenic.

So the order is:

1. Fix the moisture. The EPA says the key to mold control is moisture control.
2. Remove the mold. Scrub hard surfaces with detergent and water, and dry completely. Porous materials such as ceiling tiles and carpet may have to be thrown away.
3. Then, if you want, run an air purifier to help with airborne particles while the house dries out and afterward.

If you buy an air purifier for mold, get one with a true HEPA filter. The EPA says a HEPA filter can theoretically remove at least 99.97% of dust, pollen, mold, bacteria and other airborne particles with a size of 0.3 microns. That size is the hardest to catch, so larger and smaller particles are captured at higher rates.

The EPA notes that portable air cleaners often achieve a high CADR by using a high-efficiency particulate air (HEPA) filter. When you compare boxes, look for the word HEPA itself and a listed CADR, rather than vague claims about "purifying" or "eliminating" mold.

CADR: the number that tells you if it's big enough

CADR stands for clean air delivery rate. The EPA says the number is meant to help you select an air cleaner based on the size of the area it will run in. Note that the CADR rating system is for particles only, which is fine for spores.

Some boxes list three CADRs: tobacco smoke, dust and pollen. The EPA says these represent small-, medium-, and large-sized particles, respectively, and suggests choosing a high tobacco smoke CADR to filter the smallest particles.

Table: EPA portable air cleaner sizing for particle removal, assuming an 8-foot ceiling. Source: EPA Guide to Air Cleaners in the Home.

To use it, multiply your room's length by its width. A 14 by 16 foot bedroom is 224 square feet, so look for a CADR above 130, and closer to 150. The EPA says higher ceilings may call for a higher CADR.

Getting the most from a purifier

• Run it a lot. The EPA says the longer the air cleaner runs, the more air it filters.
• Put it where you spend time. The EPA suggests placing the unit in the room(s) you spend the most time in, away from curtains and anything that blocks airflow.
• Change the filter. The EPA says all filters need regular replacement; a dirty, overloaded filter won't work well.
• Upgrade your HVAC filter too. For central systems, the EPA says to select a filter rated at least MERV 13 or as high as your system will accommodate.

Some machines sold for mold, odor or "air purifying" make ozone on purpose. The EPA advises against them.

• At levels within public health standards, ozone does not effectively remove viruses, bacteria, mold, or other biological pollutants.
• To actually decontaminate air, ozone would need to be 5 - 10 times higher than public health standards allow.
• Ozone may have no effect on contaminants embedded in porous materials such as duct lining or ceiling tiles, even at high concentrations.
• Health: when inhaled, ozone can damage the lungs, and relatively low amounts can cause chest pain, coughing, shortness of breath and throat irritation.

The EPA's air cleaner guide says to avoid portable air cleaners and furnace/HVAC filters that intentionally produce ozone, and notes that devices using electrostatic precipitators, ionizers, or UV lights without adequate lamp coatings may also emit ozone. Its conclusion on ozone generators: the public is advised to use proven methods of controlling indoor air pollution.

If a contractor offers ozone "fogging" as the fix for mold in your home, ask what they plan to do about the moisture and the visible growth.

Small patch (under about 10 square feet). The EPA says that if the moldy area is less than about 10 square feet (less than roughly a 3 ft. by 3 ft. patch), in most cases you can handle it yourself. Wear the EPA's minimum gear for small areas: gloves, an N-95 respirator, and goggles/eye protection. The EPA recommends long gloves that extend to the middle of the forearm and goggles that do not have ventilation holes. Our vinegar vs bleach for mold guide walks through the steps.

Bigger than that, or after a flood. If there has been a lot of water damage or mold growth covers more than 10 square feet, the EPA points to its professional remediation guidance. It also says do not run the HVAC system if you know or suspect that it is contaminated with mold, since it could spread mold through the building.

Keep humidity down afterward. The EPA says to keep indoor humidity below 60 percent (ideally between 30 and 50 percent). In humid parts of Texas, a dehumidifier does more for mold than an air purifier; see our dehumidifier for mold guide.

The CDC says that for some people, mold can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes, or skin rash, and that people with asthma or mold allergies may have stronger reactions. An air purifier is not a medical treatment, and a mold test can't tell you whether mold is making you sick. If you're worried about symptoms, see a doctor. TDLR also recommends that people consult a health care provider if they're concerned about mold's effects on their health.

If you can smell mold but can't find it, a licensed mold testing company can do an assessment. If you already know where the mold is and it's large, a licensed mold removal company does the cleanup. Texas keeps those jobs apart: a license holder may not perform both mold assessment and mold remediation on the same project. TDLR says that in most instances, areas of visible mold less than 25 contiguous square feet may be cleaned by people who aren't licensed.

Browse companies in Dallas, Austin or anywhere in Texas, check any license with our license check, and see how we verify every listing. If you're unsure whether you need testing at all, read is mold testing worth it.