There are spores everywhere, floating in the air outside, in your office and in your house. There is no way to completely avoid them. But inhaling mold spores could lead to medical problems. The Centers for Disease Control (CDC) found that people with mold sensitivity can experience upper respiratory symptoms, increased asthma symptoms and even skin irritation when exposed to mold and mold spores. The World Health Organization (WHO) examined multiple studies and found that the presence of mold was associated with respiratory symptoms and exacerbated asthma symptoms.

Read more about a new technology that can completely destroy mold.

One way to deal with the presence of spores in your house is to use an air purifier. A lot of companies claim to have the best air purifier for mold, so it is important to understand the technology behind each type of air purifier and how well that purifier will work to remove mold and other microscopic spores to improve your indoor air quality.

The right air purifier for you will depend on your particular situation. Are you remediating a mold problem in your house? Do you suffer from mold allergies or asthma? Does someone in your house have a compromised immune system? We will examine the different types of air purifiers available and determine what is the best air purifier for mold and other spores.

Mold, mildew and other spores

What is mold, and what is the difference between mold and mildew? Mildew is simply one type of mold. All molds are fungi. In nature, molds and other fungi help break down dead organic matter. In your house, their effects are not so beneficial. They can cause damage to the surfaces they are growing on. But the more immediate threat from household mold comes from spores.

A spore is the reproductive unit of a fungus. Almost all spores are unicellular. According to the University of Central Florida, they range in size from 3 to 40 microns, which means they are all microscopic. While there are different ways spores move around, most mold spores simply drift around in the air until they land on a surface. If that surface is very dry, cold or otherwise unsuitable for the spore to begin mitosis, then nothing else happens. But if the surface is warm and moist, the spore begins dividing and eventually grows into more mold, which produces more spores, and so on. That is where you can develop indoor air quality problems.

Once mold starts to grow in your house, it will spread and continue to emit spores. The spores in the air are what cause health problems for people with mold sensitivities and weakened immune systems.

How can an air purifier help with mold?

It is very important to understand that an air purifier will not solve an existing, visible mold growth problem in your house. If you have visible mold growing somewhere, it has to be remediated; physically cleaned, usually with a bleach solution. If it is growing on a soft surface like a carpet or foam, the surface must be removed and thrown away, because it is impossible to clean mold out of the many tiny crevices in a soft surface. The source of the moisture that allowed the mold to grow (a leaky pipe, damp walls from a flood or simply high humidity) must be removed as well.

An air purifier also will not remove every single mold spore from the air in your house. Because spores are so ubiquitous, it would be futile to even try. Spores are everywhere. However, if you are remediating a mold problem you probably have a lot of mold spores in the air. For an immediate need, you may consider a high capacity, industrial air purifier with a high flow rate (e.g., 600 cfm) if there is extensive damage like in a flood situation. An air purifier can help reduce the concentration of spores in the air during the initial cleanup, though filters may need be changed frequently. An air purifier can also help right after the cleanup to remove lingering mold particles. This can help remove some of the “musty smell” associated with a mold problem.

Using an air purifier, along with taking other preventive measures, can offer a long-term solution for those with mold allergies to consider. This solution can be especially helpful in places known for mold across the country or for humid regions. An air purifier can also help in common places for mold in the home like a basement. Though an air purifier can help long term for mold spores in the air, only physically cleaning up the mold and removing the moisture that allowed it to grow will solve a visible mold growth problem.

The best air purifier for mold in your house

There are different types of air purifier, each using different technology, sometimes in combination. Some air purification technology is very effective at removing mold spores from the air, some are not and some could actually do more harm than good.

HEPA filter. An air purifier with a HEPA filter is the traditional option for filtering particles from the air and can remove some mold spores. The HEPA standard is based on the ability to remove 99.97 percent of particles that are 0.3 microns in size or greater. Large particles would theoretically be trapped by a HEPA filter, as the majority of mold spores are larger than 0.3 microns. It is possible that some especially tiny spores might get through a HEPA filter. However, the real problem with HEPA filters is mold can potentially grow on the filter surface. If it is not changed regularly, the filter can actually become the host surface for all the mold spores it has trapped. The spores grow into mold and release more spores, turning the HEPA filter into a spore emitter rather than a spore remover. For example, a study in the journal Mycobiology found significant mold growth in HEPA filters [Seong Hwan Kim et al, “ Mold Occurring on the Air Cleaner High-Efficiency Particulate Air Filters Used in the Houses of Child Patients with Atopic Dermatitis ,” Mycobiology 2014 Sept.].

An air purifier with a HEPA filter is the traditional option for filtering particles from the air and can remove some mold spores. The HEPA standard is based on the ability to remove 99.97 percent of particles that are 0.3 microns in size or greater. Large particles would theoretically be trapped by a HEPA filter, as the majority of mold spores are larger than 0.3 microns. It is possible that some especially tiny spores might get through a HEPA filter. However, the real problem with HEPA filters is mold can potentially grow on the filter surface. If it is not changed regularly, the filter can actually become the host surface for all the mold spores it has trapped. The spores grow into mold and release more spores, turning the HEPA filter into a spore emitter rather than a spore remover. For example, a study in the journal Mycobiology found significant mold growth in HEPA filters [Seong Hwan Kim et al, “ PECO. Photo Electrochemical Oxidation (PECO), the technology behind the Molekule air purifier , uses a light-activated catalytic reaction to destroy the particles passing through the device. That means the PECO technology can destroy mold spores, unlike HEPA filters which trap contaminants on the filter surface. Destruction of mold spores eliminates the possibility of mold growth on the filter and reintroduction back into the air.

Photo Electrochemical Oxidation (PECO), the , uses a light-activated catalytic reaction to destroy the particles passing through the device. That means the PECO technology can destroy mold spores, unlike HEPA filters which trap contaminants on the filter surface. Destruction of mold spores eliminates the possibility of mold growth on the filter and reintroduction back into the air. PCO. Photocatalytic Oxidation is a precursor to PECO technology. While it can theoretically destroy organic molecules like mold spores, PCO is inefficient and can produce ozone, a respiratory irritant, as a side effect.

Photocatalytic Oxidation is a precursor to PECO technology. While it can theoretically destroy organic molecules like mold spores, PCO is inefficient and can produce ozone, a respiratory irritant, as a side effect. UVGI. Ultraviolet germicidal irradiation claims to sterilize air by killing bacteria, viruses and mold. The EPA suggests that to be effective, a UVGI air purifier would have to generate much more intense UV radiation than a home unit is capable of.

Ultraviolet germicidal irradiation claims to sterilize air by killing bacteria, viruses and mold. Carbon filters. Carbon filtration is used to remove airborne chemicals (specifically volatile organic compounds, or VOCs) from the air by trapping the gases on an activated carbon filter. This kind of filter is not intended for removing particles and would not be useful for removing mold spores from the air.

Carbon filtration is used to remove airborne chemicals (specifically volatile organic compounds, or VOCs) from the air by trapping the gases on an activated carbon filter. This kind of filter is not intended for removing particles and would not be useful for removing mold spores from the air. Ionizing Air Purifiers. These air purifiers impart an electric charge to particles, causing them to stick to nearby surfaces. While this technology claims to remove mold spores from the air, the drawbacks make them not worth using. The biggest problem is that as a side effect these air purifiers generate ozone, and ozone is a harmful substance that you do not want to breathe. The EPA warns that long-term ozone exposure can cause respiratory problems even in healthy people.

These air purifiers impart an electric charge to particles, causing them to stick to nearby surfaces. While this technology claims to remove mold spores from the air, the drawbacks make them not worth using. The biggest problem is that as a side effect these air purifiers generate ozone, and ozone is a harmful substance that you do not want to breathe. Ozone generators. Instead of generating ozone as a by-product, ozone generators make it on purpose. Flooding the air in your home with ozone is a bad idea that could cause health problems to anyone with asthma or other sensitivities even at low concentrations.

The final decision on what type of air purifier technology to use to remove mold spores from your house will depend on the specific need (e.g., if it is for mold allergies or immediate mold remediation), and whether you would like to use it for the long or short term.

Given the ineffectiveness or risks of the other options, the only two acceptable options are HEPA or PECO. Both types of air purifier will remove mold spores from the air, though PECO will destroy them. The major drawback of a HEPA filter is that the filter must be changed rigorously or it can end up becoming a source of mold spores. HEPA filters may be a short-term solution for removing a lot of mold spores from the air, for instance, if you are in the middle of a mold remediation. PECO technology will not have this drawback as mold spores are destroyed, which is especially important for those with mold allergies.

Mold prevention

Mold spores need moisture to become mold. Preventing the accumulation of moisture in your house is the key to preventing mold problems from ever developing to begin with.

Fix leaks. A leaky roof or plumbing system can be a source of moisture in unexpected and hard-to-reach places in your house. Repair such leaks and dry out any wet areas immediately.

Clean up after floods. A flooded basement can leave moisture in carpets, furniture, boxes and on or inside wall panels. Post-flood cleanup is a challenge, but it has to be done thoroughly, making sure everything gets dried out as soon as possible.

Proper ventilation. Kitchens and bathrooms should have proper ventilation to vent moisture outside the house. Otherwise, moisture can build up on the walls and ceiling and allow mold to grow.

Keep humidity low. Basements are often damp even in climates that are not especially humid. Running a dehumidifier to keep humidity low is a key step in preventing basement mold. In very humid climates, air-conditioning acts as a dehumidifier and helps keep humidity levels in the whole house low.

Finding the best air purifier for mold in your home will usually come down to considering a device with HEPA or PECO technology. In conjunction with taking the right preventive steps, an air purifier can go a long way to reduce the levels of mold allergens in your home.