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Basements are renowned for stale air. It’s not just a simple nuisance, but it may pose a health risk. Basement air quality may be the worst in your house, especially if you have an unfinished basement. The musty smell is symptomatic of air pollution capable of causing adverse health effects. The air quality may even spread to other parts of your home. Placing the right kind of air purifier in your basement can help offer relief for unhealthy air caused by various types of pollutants.

Choosing the best air purifier for your basement

There is a variety of technology to pick from in the market of air purifiers, let’s look at the breakdown of how each one works to combat unclean basement air.

Photo Electrochemical Oxidation (PECO) air purifier

Photo Electrochemical Oxidation (PECO) is the technology used in Molekule air purifiers. It was developed over a period of 20 years to clean the air in an entirely different way: Instead of trapping airborne allergens and pollutants like mold or VOCs on filters, PECO is designed to destroy them through a catalytic reaction.

In a humid basement where mold can grow, the possibility of mold growth on a filter surface is greater than usual. The Molekule PECO technology prevents this from happening, as airborne mold spores are destroyed. The VOCs that form unpleasant odors, as well as some dangerous airborne chemicals, are also destroyed. The PECO technology has been independently tested for its effectiveness against VOCs and proven to destroy microbes like mold, which would make it an ideal choice for basements where these pollutants are common. Visit our website to purchase a Molekule air purifier for mold.

High-efficiency particulate air (HEPA) air purifiers

HEPA filters are typically rated on how well they trap airborne particles that are a diameter of 0.3 microns in size. The basement air purifiers advertise the removal of 99.97% of particles at that size. However, HEPA filters used alone only trap particles on the filter surface, which is problematic for mold spores or bacteria that can continue to safely proliferate on the filter, given the right conditions. Because of this possibility, HEPA filters should be changed on time, especially in a humid or moist basement where mold and other harmful particles are likely to grow. Though HEPA filters are an acceptable option for a basement, they are designed to remove particles and not gases. If musty odors are a problem, then a HEPA filter would need to be used as part of a hybrid unit with a second technology that can deal with smells (usually a carbon air filter, as discussed below).

HEPA with UV light

Some HEPA air purifiers are coupled with ultraviolet (UV) light. While any potential mold or bacterial growth on the filter surface may be slightly mitigated by the UV light, it is not effective as a total solution. Not only that, but some UV technologies generate toxic ozone, exacerbating or causing problems to respiratory health . Though a HEPA filter would be an acceptable option, the added feature of ultraviolet light would only minimally reduce the risk of mold growth on the filter surface and could pose a danger, especially if the basement is used as a living space and you are in close proximity.

Carbon Air Filters

Carbon filters are designed to remove gases through a bed of activated carbon , removing pollutants by means of chemical adsorption. Carbon air filters specifically address airborne chemicals known as volatile organic compounds (VOCs). Odors and musty smells in a basement are made up of VOCs that are released into the air (though some harmful VOCs are odorless).

They filter the air until the carbon sheet becomes saturated and needs replacement, which can be expensive and fairly frequent, especially if the weight of carbon in the unit is small. It is also possible that VOCs trapped on a carbon filter can “off-gas,” or release back into the air, because of their chemical properties. Unfortunately, carbon air filters cannot remove particulate pollutants like allergens, pollen or dust, meaning they have to be used in conjunction with other methods to improve air quality. Notwithstanding, carbon filters are an acceptable option for musty odors and other VOCs in basements, though they are not foolproof as gases can “unstick” from the filter surface.


Photocatalytic Oxidation (PCO), the technology used in PCO air filters, is a process that claims to use UV light and titanium oxide to change the properties of particles at the molecular level. Purifying air in this way attempts to clear VOCs from air, but does not address particulate matter (dust, mold, pet dander). Another drawback of this method is the production of formaldehyde, a known human carcinogen. The effectiveness of PCO on odors and musty odors in a basement remains in question, and the technology does not have an effective process for removing particles like mold spores and dust.

Ozone Generators

This type of air purifier works by generating ozone, which reacts with VOCs to change them chemically and make them less odorous. However, this technology produces harmful levels of ozone that can be detrimental to your respiratory health . If you use your basement as a living space or spend a lot of time there, the risk of ozone exposure could negate any potential benefit of the technology.

Why basement air tends to be awful

Approximately 32% of American homes have basements . Many people have converted their basement into a regular living space. With significant time being spent in basements, it is important to focus on air quality in your basement, particularly as they often have many problem points that can contribute to poor indoor air quality, such as poor ventilation and air circulation.

Problems with basements:

The problem with basements is that they are a perfect breeding ground for mold. They are also the part of the house most commonly associated with radon, dust, and volatile organic compounds (VOCs) each of which pose distinct problems.

Mold – High indoor humidity levels and too much moisture in the basement is perfect for common molds such as penicillium and aspergillus fungi. To make matters worse, the gypsum in drywall commonly used within the home may become a breeding ground for mold strains like Chaetomium, Stachybotrys, and Ulocladium.

VOCs – Basement air has a lot of risk factors for the presence of VOCs, chemicals which infiltrate the air, sometimes very obviously, with a potent stink, and sometimes without any odor at all. Recent studies have shown that VOC levels are 2-5x higher indoors than outdoors, and likely higher in basements, due to poor airflow and a tendency to be the storage space of unused old materials and paints.

Radon – Radon is another challenge for basements. It is extremely poisonous to breathe and may increase the risk of lung cancer. Radon is a naturally occurring radioactive gas that accumulates in the soil. It primarily enters the home through cracks in the foundation. Radon may also be found in water and building materials.

Dust – Dust and other particle pollution lower the air quality in the basement, especially because they are often neglected when it comes to cleaning. While dust can be seen by the naked eye, particle pollution is small enough to contaminate otherwise clean air, originating from chemical cleaners, stoves, fireplaces, and industrial pollution.

Stagnant air – Lastly, stagnant, slow-moving basement air exacerbates pre-existing issues with air quality. Because basements are generally ill-equipped for ventilation, air pollution accumulates quickly, making it very likely the air has a high concentration level of irritants and toxins.

The serious health risk factors caused by basement air:

We breathe in roughly 2 gallons of air a minute, harmful particles included. Contaminated basement air poses particular threats to our health. Persistent exposure to VOCs, radon, and particle pollution cause a wide range of health problems. Combined they can exacerbate serious pre-existing conditions.

The pollutants found in basements may cause inflammation, especially in people with medical conditions like asthma, sensitive airways or allergies.

The Center for Disease Control and Prevention (CDC) states that “if you can see or smell mold, a health risk may be present.” Mold has been linked to increased rates of respiratory issues, such as allergies and asthma , in otherwise healthy people.

What actually causes the poor air quality in basements

A common complaint about basement air is its odor. The “musty basement smell” is caused by a cocktail of impurities such as mold, VOCs, and mildew, a smell exacerbated by stagnant airflow.

Basements with carpets may be particularly stinky. Moisture can seep up through the foundation through a phenomenon known as “capillary action.” This creates a damp environment that smelly molds thrive in. Furthermore, mold spores are very sticky and once they settle on carpet fibers they are extremely difficult to completely remove. As the spores start to grow in the moist carpet they emit dangerous substances such as mycotoxins and smelly VOCs. Then without adequate airflow in a stagnant basement the level of pollutants accumulate over time.

Current home design is focused more on reducing air leakage to keep warm air in and reduce heating bills. By design, this lack of outward air flow causes poor ventilation, and aids in basement air stagnation and moisture buildup. These factors combined create an ideal environment for mold, mildew and dust mites to live in.

What most people do wrong to improve basement air:

Many have realized the problematic nature of their basement air, and have tried to cover up or fix the mustiness. These efforts, unfortunately, can be misguided and lead to improper solutions that don’t remedy bad basement air.

For example, many people use air freshening sprays to cover up the musty basement smell. Almost all sprayable air fresheners are composed of VOCs which are often toxic. Their purpose is to cover native smells with even more powerful scents. While this may work for a quick fix, it only hides the issue, while further polluting the air.

Basements and air quality: Location matters

Your climate can have a significant impact on the air quality in your home.

Areas near large bodies of water naturally experience very high humidity. The level of moisture in your home is strongly linked to that of the air outside, so homes in wet areas have a greater chance of holding more moisture and developing mold.

For those living in more developed urban areas, toxic air particles from car exhausts and industrial plants can find their way into your home, lingering in the still, uncleaned basement air.

How Do I Keep Basement Air Clean?

Basement smell may come from numerous pollutants. Luckily there are a variety of ways to clean basement air, making your basement safer and less noxious.

One way is to improve your basement air ventilation. Weather permitting, opening up any and all windows or doors can increase airflow and reduce the build-up of pollutants.

Adjusting the humidity in the basement is another way to decrease the risk for air pollutants and musty basement air. The EPA recommends keeping indoor humidity between 30-50 percent, measurable by humidity gauges available at most hardware stores. Humidity can be increased using a humidifier. To decrease humidity, you can open a window, use an air conditioner or a dehumidifier.

Excess moisture can increase the risk for mold to grow and should be addressed to keep basement air clean. There are a wide variety of issues in building design and construction maintenance which can contribute to moisture control problems, and some solutions may require simple or serious home renovations.

If there is any existing mold in your basement, it should be removed, which can be an effective method to remedy basement air. Far from a simple task, the CDC recommends you take careful steps or hire a mold removal specialist. Mold is tenacious, returning even after repeated cleaning unless the environment itself is treated for prevention.

Removing radon from the basement is a more difficult task, as the source is always in the soil outside of the house. The first step is to buy an inexpensive test kit to determine if there is a radon problem. If there is a problem it is best to hire a contractor who specializes in fixing radon problems.

Air purifiers are an effective and relatively simple solution for almost all basement air quality issues that do not include radon. New technological advancements have made purifiers available which efficiently eliminate particles, VOCs, bacteria, viruses and mold spores.

Can an air purifier remedy basement air?

Air purifiers can help combat the pollutants which cause musty, noxious basement air that is hazardous to your home.

Poorly ventilated air is eerily still, giving biological matter a great opportunity to settle and grow. Air purifiers prevent high levels of contamination, by both ventilating and cleaning the air, creating a current and getting the air moving again for improved air quality.

Specific air purifier considerations for basement use

The specific air purifier unit you choose to improve musty basement air may vary according to your basement layout, how you use that space, and the main problems with your basement air.

The size of your basement will also help decide which approach is most effective. A larger basement with more square footage may need a unit capable of processing a large volume of air. Choosing a compact size air purifier for a large basement may yield unsatisfactory results.

Basement space that functions as an apartment or bedroom should have special consideration when purchasing an air filter. For full scale, constant-occupation living spaces, a high-quality air purifier should be used with special avoidance of those that may produce harmful chemicals. Additionally, some air purifiers are exceptionally noisy.

Molekule: Our solution

Molekule offers a solution that effectively mitigates the causes of poor basement air quality using proprietary PECO technology. Molekule can replace the air in a 600 square foot room once an hour, using a 360° air intake to pull in air from all sides and project clean air in every direction. Its dual filter technology proves effective at removing particles, mold, pet hair and odor, the triple threat of basements, doing so quietly, beautifully and unobtrusively – perfect for basements used as living spaces.

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