Air Purifier vs Dehumidifier for Mold

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Written By Jamila W.

If you are dealing with mold issues, you might be wondering whether an air purifier or dehumidifier for mold is better for your situation. Both devices can help reduce mold growth, but a dehumidifier is an essential device that reduces the humidity and water vapor that drives mold growth. In this article, we explain the difference between an air purifier vs a dehumidifier and why the dehumidifier is going to be the better buy for a mold problem.

Air Purifier vs Dehumidifier for Mold: What’s The Difference?

When it comes to mold, air purifiers can help by removing mold spores from the air before they have a chance to settle and grow on surfaces. However, air purifiers do not reduce the moisture levels in the air, which is necessary to prevent mold growth. Therefore, if you have high humidity levels in your home, you may need to use a dehumidifier in addition to an air purifier. Conversely, dehumidifiers do not remove mold spores from the air, meaning they can still settle on surfaces and grow if the humidity levels are not kept low enough. 

Air Purifier vs Dehumidifier: Comparison

Air PurifierDehumidifier
What is it:An appliance that removes particulate and gaseous pollutants from room airAn appliance that removes water vapor from room air
Purpose of appliance:Purification of indoor air from pollutants that degrade air qualityReducing humidity in indoor environments and preventing mildew and mold
Initial release:1860s1902
Developers:Charles Anthony DeaneJohn Stenhouse The Manhattan ProjectWillis Carrier (The inventor of air conditioning)
Technologies used:Mechanical filter,Ionization,Catalytic oxidation,Chemisorption,Ultraviolet germicidal irradiation Thermal condensation,Absorption/desiccant,Membrane, Ionic membrane
Types of particles removed:Mold DustPollenPet danderFine particulatesInorganic gassesVolatile Organic Compounds (VOCs)Water Vapor 
Applications: Home air purificationCommercial air purificationAir cleaning in sensitive environments like hospitals and  electronics manufacturing environmentsReduction in humidity in residential and commercial environmentsReducing mold and mildew in propertiesRemoval of moisture and prevention of mildew in building sitesMoisture removal in flooded indoor spaces

What is Mold?

Mold is a biological structure that is formed by certain types of fungi that are everywhere. Fungal spores thrive in persistently damp and humid environments and grow on any organic material if moisture and oxygen are present. Mold grows on surfaces like paper, wood, carpet, plaster, and insulation in a property. 

Mold is a progressive problem, and as it spreads it digests and destroys the materials it grows on, even leading to structural damage. As mold proliferates, fungal spores are released into the air which can be inhaled by building occupants, causing a variety of health consequences. 

It is impossible to eliminate mold, but its growth can be controlled by controlling humidity levels in an indoor environment. By reducing the levels of moisture available, mold growth can be slowed. 

Mold Growth, Humidity, and Air Quality

The fungal spores released by mold are major indoor air pollutants. Excess humidity is also a factor that impacts air quality and potentiates mold growth. Sources of excess humidity in indoor spaces include cooking, bathing, showering, clothes dryers, condensation, and humidifiers.

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In the presence of high humidity, the concentration of these spores suspended in indoor air increases. If the Indoor Relative Humidity (IRH) is above 60%, there will be enough moisture available for mold growth. Ideally, IRH should be kept between 30 and 50%, to prevent the development of mold and ensure that breathing is comfortable. 

Mold Odor 

Mold generates distinctively pungent and musty odors that indicate that it is present in a room. Often the earthy odor is the first sign that a property has a mold or mildew problem. This stale smell lingers in humid environments where the air becomes stagnant. 

The mold odor molecules are microbial volatile organic compounds (mVOCs), carbon-containing molecules that have an unpleasant smell and can be harmful.

Health Consequences of Mold Exposure

Mold not only causes structural damage to properties but also causes a wide variety of health problems, which can become chronic or progressive.  Health issues associated with prolonged mold exposure include: 

  • Non-specific malaise, lethargy, dizziness
  • Fatigue
  • Nausea
  • Headaches
  • Allergies
  • Upper and lower respiratory tract irritation, inflammation, and infections
  • Asthma symptoms

mVOCs also cause respiratory and neurological problems, even where visible mold growth is limited. Certain groups of people are particularly vulnerable to the effects of mold including immunocompromised individuals, seniors, and young children.

Domestic mold growth is a key contributor to the adverse health effect of poor indoor air pollution, making it essential to keep relative humidity and condensation down to limit its growth. Aside from regular cleaning and good ventilation of your home, appliances like air purifiers and dehumidifiers play a role in removing mold spores from the air and preventing mold growth.

How Do Air Purifiers Prevent Mold?

Air purifiers do have a role to play in combatting the common problem of mold. These appliances can cleanse the indoor air of the fungal spores that give rise to mold. However, they cannot remove water vapor from indoor air, which is the key driver of mold growth. But by removing these airborne contaminants, mold development, and spread are suppressed. 

How Air Purifiers Work

Air purifiers are fan-powered machines that pull air and remove airborne particles like mold spores, dust mite populations, pet dander, and mVOCs, releasing clean air into the environment and improving air quality. They do not remove moisture. The removal of mold spores reduces mold growth. These devices use a variety of technologies that can capture particles, retain, or destroy mold, including:

Mechanical filtration: This is the most common type of air cleaning for optimal indoor air quality and uses a fibrous filter to trap mold spores. High-Efficiency Particulate Air (HEPA) filtration is an industry-standard air filter that can trap 99.97% of particulates of 0.3 microns in diameter. For comparison, mold spores have a diameter of 2 to 100 microns.

Electrostatic Precipitation (ESP): ESP air purifiers trap air pollutants using electrostatic attraction to charged plates within the unit. 

Adsorption media: Volatile organic compounds like mVOC are gaseous, and cannot be trapped in a filter. However, adsorption media like activated carbon filters, absorbs these gases. The adsorption media is usually coated on a filter material to maximize the surface area for trapping gasses. 

Catalytic oxidation: This more recent technology uses a UV light-activated titanium dioxide catalyst to generate free radicals that destroy air pollutants including mold by oxidation. The main commercial versions of this technology are photocatalytic oxidation (PCO) and photoelectric catalytic oxidation (PECO). 

Ionic air purifiers: These air purifiers electrically charge air, generating negatively charged particles that attach themselves to indoor air pollutants and move them to the charged surface where they are retained. 

The Benefits of Air Purifiers for Mold

Air purifiers are effective at reducing the amount of mold spores in your indoor air. By removing the spores, the air purifier improves indoor air quality and reduces your risk of mold exposure. This is particularly beneficial if you have allergies or existing health problems that mold aggravates. An air purifier can also remove unpleasant mold and mildew odors and prevent spores from setting on damp clothes or surfaces. 

The specifications of the air purifier will determine its effectiveness in reducing mold in your home environment. The best air purification technology for mold is HEPA filtration, due to its high efficiency at trapping mold spores. Air purifiers combining a HEPA filter and an activated carbon filter can remove airborne particles and tackle mVOCs. The air purifier also needs to be appropriately sized for the room where it will be removing airborne particles. 

How do Dehumidifiers Prevent Mold?

Dehumidifiers are the primary solution for combatting the problem of mold in properties. Aside from correcting structural problems like leaks, using a dehumidifier is the most effective way to reduce humidity in buildings and starve mold of the moisture required for its proliferation. 

How Dehumidifiers Work

Dehumidifiers remove excess moisture from the air by passing the room air intake over an actively cooled coil, much like an air conditioning system, to control humidity. As the moist air passes over the cold coils, moisture from the air condenses into water droplets that are collected or drained. Most consumer dehumidifiers have sensors to measure indoor humidity levels and automatically switch on and off to maintain a consistent humidity level. 

Benefits of Dehumidifiers for Mold

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Humidity is the main driver of mold growth, so removing water vapor dehumidifiers can be very effective at controlling mold. By keeping the humidity levels below 60%, you can significantly reduce the risk of mold growth. A dehumidifier pulls moisture from the environment but cannot remove mold spores from the air or change room temperature. 

By removing excess moisture from the air, dehumidifiers can also help to improve air quality as common allergens like bacteria, viruses, and dust mites are less persistent when air humidity falls.

Prevent Excess Moisture to Reduce Mold

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It is important to note that air purifiers and dehumidifiers are not a substitute for proper mold remediation. If you have a mold problem in your home, it is important to identify and address the source of the moisture and remove the mold properly. Also, indoor condensation generated by domestic activity is a massive driver of mold growth, so consider taking the following steps to reduce the amount of excess moisture released into indoor air:

  • Ensure that vented devices like clothes dryers have a vent that directs condensation outside of the building. 
  • Cover saucepans when cooking
  • Close curtains at night, so that water vapor does not condense on the cool surface of windows
  • Install an extraction fan in your bathroom to remove water vapor from bathing or showering
  • Avoid drying clothes indoors
  • Open windows in different parts of your home to increase cross-ventilation and remove harmful pollutants

With these structural and activity-related issues addressed, homeowners can expect improvement in odor mold and mildew growth in their property by using a dehumidifier and air purifier in the same room.

Closing Thoughts

In general, air purifiers and dehumidifiers can help reduce mold growth, but they work in different ways. Some models also have additional features like one or more filters and air purifiers, and technology to monitor a room’s humidity levels to improve indoor air quality. Air purifiers and dehumidifiers can be used as preventive measures to reduce the risk of mold growth, but they cannot eliminate mold that has already started to grow.

If you have high humidity levels in your home, a dehumidifier is essential for removing moisture and preventing mold growth. However, an air purifier can also be beneficial to trap particles and remove mold spores and airborne allergens, and smoke particles from the air to improve overall indoor air quality. Using both devices together provides the best protection against mold growth.