What are VOCs? Why are VOCs harmful?

VOCs are Volatile Organic Compounds, or odors. They are super tiny chemicals that are lighter than air. They are easily released from their sources into the air around them. Importantly, “organic” refers to carbon-based chemicals, not what you might normally think of (natural or organically grown foods, for example).

They are gasses, and many have harmful properties— formaldehyde is the most dangerous example (it is a carcinogen) and is found in the home in glues holding furniture together, new carpet or vinyl flooring, sealants, stains, and finishes on wood furniture or flooring, engineered wood and particleboard, paints, area rugs with synthetic backing and glues, and cleaning products. Formaldehyde and benzene are VOCs released from daily indoor products and are both known carcinogens. There are thousands of other VOCs which contribute to asthma, allergy, frequent headaches, and lung issues.

The “new house smell” is simply VOCs off-gassing into the air. Interestingly, you can’t always smell them, because your nose gets used to certain scents, or can’t detect them at low levels.

Can an air purifier help with allergies?

Yes, an air purifier can help with allergies in three ways. First, it can trap large particles like pollen and pet hair on its pre-filter. Second, an air purifier with a HEPA filter is great at capturing smaller particles like mold spores, dust mite debris, and even cooking or wildfire smoke particles that can irritate the lungs, nose, and throat. Finally, an air purifier with activated carbon or minerals can remove irritating VOCs from the air, which also contribute to allergy.

Can an air purifier help with mold?

Yes, an air purifier can help with mold in three main ways. First, it can capture mold spores that are floating freely in the air, reducing the chances they will land and overgrow on a humid or damp area. Second, if you’re allergic to the mold, it can reduce your exposure as it captures these spores. And third, an air purifier with activated carbon or minerals can adsorb mold-associated VOCs and odors from the air, making it smell less musty during recovery from a mold problem. Removing the source of mold is also very important; having a mold inspection and remediation done, or using a dehumidifier to prevent excess dampness are good ideas in conjunction with using an air purifier for mold.

Can an air purifier help with odors?

Yes, if it has activated charcoal, zeolite, or another gas adsorbent! Gasses are not particles, and therefore cannot be captured meaningfully by a HEPA filter. An adsorbent is used instead. Adsorption is a chemistry-based process that works when a gas clings to the surface of the adsorbent, where it stays trapped. Activated charcoal is very good at capturing a wide range of odors (also called VOCs) from the air.

A simple carbon cloth will not capture much, but if a pound or more of activated carbon is added, that increases the ability to adsorb odors. Sometimes, mineral mixtures are added to activated charcoal to increase the types of VOCs that can be adsorbed from the air. Potassium iodide, potassium permanganate, and zeolite are three different mixtures that are commonly added because each has a different pore size that can adsorb different chemicals better than charcoal alone. Zeolite is capable of adsorbing formaldehyde, which is important, because charcoal cannot do it on its own.

I also recommend removing VOCs from the source— purchasing low-VOC furniture and decor, and not using scented products (or choosing safer ones).

Are HEPA-style or 99% HEPA filters the same as regular HEPA filters?

No! The terms HEPA-style, HEPA-like, 99% HEPA, and others, are not real HEPA filters. These do not filter particles with the same efficiency as HEPA filters, and may not filter small particles at all. HEPASilent is the exception so far; it is a more loosely woven, charged filter made by BlueAir and importantly, third party testing and its CADR numbers back up its effectiveness.

Is HyperHEPA or UltraHEPA better than regular HEPA?

No, these are marketing tactics. If you look closely, these filters are just H12, H13, or H14 HEPA filters. They all remove particles 100 times smaller than 0.3 microns— that’s the definition of HEPA. Due to complicated physics, 0.3 microns is the hardest size of particle to capture. It’s actually easier to capture particles both larger and smaller than this. Some of the brands listed above make the claim their HEPA filters are better than others, but I’ve decided not to hold it against them because their machines work really well in third party testing to protect people from dangerous particles and gasses. Big of me, I know! ;)

What is an ULPA filter?

ULPA filters are Ultra Low Penetration Air filters. They can actually capture even more particles than HEPA, but, they do not work as well as HEPA filters, because they are so tight, that air has such a hard time getting through them. They have a very low CADR (clean air delivery rate). They may sound better, but they are not recommended, because they clean very small amounts of air.

What is a PECO air purifier?

PECO stands for PhotoElectroChemical Oxidation. It oxidizes micro-organisms, effectively killing them. This technology has been around for decades, but in 2016, was added to the Molekule air purifier. Unfortunately, it was found in multiple tests unable to filter out harmful particulate matter like PM 2.5 or other gasses nearly as effectively as regular HEPA filters can. The Molekule company was forced to retract these claims. While it is an interesting technology, with potential future applications, it remains just not as effective as regular HEPA filtration. The Molekule filter now has a HEPA filter and a PECO filter. This is a major and well-publicized version of healthwashing.

What do CADR and CFM mean?

CADR = Clean Air Delivery Rate. CFM = Cubic Feet per Minute. These are two metrics commonly used to measure how effective an air purifier is.

The CFM is how much of a room’s air volume is filtered each minute. A general rule of thumb is to look for at least 100 CFM for every 250 square feet of space.

The CADR is the CFM multiplied by the efficiency of the filter. It only applies to particulate matter (it does not measure how well VOCs or microbes are filtered). The CADR is a fine measurement if the purifier has a true HEPA filter. It is not useful for a purifier with a very high CFM but a non-HEPA filter: this would mean that air moves through rapidly, but doesn’t actually get clean. A good rule of thumb: choose a HEPA air purifier with a CADR 2/3 of your room’s area. A 20 x15 square foot room has an area of 300. So, a CADR of 200 minimum would be ideal.

These are important measures to consider, and typically play in to how well an air purifier does in testing. But, it’s not the whole picture: the HEPA filter density matters, too. This is why I rely on real-world testing rather than exclusively on these numbers.

What is UVGI?

UVGI stands for Ultraviolet Germicidal Irradiation. This technology does have the ability to kill microbes, however, in most home air purifiers, the air flows by it too quickly, leaving inadequate contact time for it to be effective. UVGI also does not address the main issues in most homes, which are particulate matter and VOCs, rather than microbes.

What are air purifiers with ionizing technology?

Ionization is a very popular technology add-on for air purifiers. If they are strong enough, they emit ions, which stick to particles in the air, and cause them to become “heavier” and stick to items in the room. Sure, the air is cleaner temporarily, but now the particulate matter is settled on your stuff. Worse, if an ionizer is strong enough to do this effectively, it is also generating ozone, which is toxic to your lungs and causes inflammation.

Why are air purifiers with ozone generation unsafe?

Ozone, O3, is the free radical version of oxygen. It is highly reactive with particles in the air, and also highly reactive with cells in your body. Breathing in ozone can cause lung inflammation and respiratory issues.

What decibel level is reasonable for air purifiers?

Air purifiers are meant to be run 24/7 on their low setting, unless during times of high air pollution (wildfire, burning food indoors, or acute off-gassing from new furniture, for example.) I consider anything under 50 decibels (dB) to be quiet enough for bedroom use. For reference, 50dB is about the sound you’d hear in a quiet office, or coming from a quiet refrigerator. It is generally considered a reasonable and safely quiet level for sleep.

When sound is unwanted, and affects the health and well-being of people or other living creatures, it meets the definition of noise pollution. The EPA confirms that it’s not just an annoyance, but is as important to your health as other types of pollution are, like air or water pollution. Excess noise, especially at night, can actually contribute to heart attack, and have negative impacts on cardiovascular health, including high blood pressure.

Do air purifiers remove radon?

No! A VOC adsorber might capture a very tiny bit of radon, but the only way to truly deal with radon is to test for it, then have it mitigated by a professional company. They usually install a radon release tube. Radon is very dangerous and is the second leading cause of lung cancer, so this is a life-saving point!

Do I still need to dust with an air purifier?

Yes, but less often. Air purifiers are very efficient at capturing airborne dust, but are not strong enough to lift dust that settles on surfaces in your room off into the air.

What are the best air purifying plants?

680 of any plant you like! The 1989 NASA study that’s often referenced as proof that plants can purify the air is wildly overstated. While it’s true that plants can remove some VOCs and carbon dioxide, this study only applies to a small, sealed, space station style environment. In a regular house, you would need about 680 plants to replicate those results. See my short video about it here.

Do probiotic air purifiers work?

Maybe on a minuscule level. While I love the idea of probiotics incorporated into homes, this is not an effective way to remove fine particulate matter (PM 2.5) or VOCs, which can have serious consequences for cardiovascular, lung, and cognitive health, from your air. Until I see a third party validated measurement of meaningful PM 2.5 reduction by these machines, I consider these a form of healthwashing.

Do moss-based air purifiers work?

Maybe on a minuscule level. Until I see a third party validated measurement of meaningful PM 2.5 reduction by moss, I consider these a form of healthwashing. They may be pretty and certainly aren’t doing harm, but aren’t protecting you, either. In a regular house, you would need about 680 plants to meaningfully reduce air pollution. See my short video about it here.

Do water-based air purifiers work?

Maybe on a minuscule level. Until I see a third party validated measurement of meaningful PM 2.5 reduction by water, I consider these a form of healthwashing.

Why is it hard to find a good air purifier?

Air Purifiers are high tech, expensive, increasingly important for people to have, and work on an invisible level. Unfortunately, this creates a perfect storm for healthwashing, and the number of air purifier companies making false claims to trick customers into thinking they’re buying a superior product has been well-documented as a problem.

Are there any 3rd party certifications for air purifiers?

Very few. And, the ones that exist are voluntary. Air purifiers are a very inconsistent and unregulated industry, especially for portable in-home air purifiers that the majority of people need.

CARB (the California Air Resources Board) and UL (Underwriters Laboratories) are third parties that verify that air purifiers don’t generate ozone.

AHAM (Association of Home Appliance Manufacturers) has standardized the clean air delivery rate (CADR) but it only applies to how well a purifier can clean air with dust, pollen or tobacco smoke (not VOCs, viruses, or other contaminants).

HEPA is not a 3rd party certification, but legally, a company can only say their filter is a HEPA filter if that is indeed true.

Can I depend on 5-star reviews to find a good air purifier?

Ratings that rely on 5-star customer reviews, or blogs that aggregate customer reviews, are uniquely unreliable for air purifiers because the placebo effect comes in to play — buying something expensive certainly has the power to make you feel like your air is cleaner (even when it isn’t). For example, the $800+ Molekule had great reviews before it was discovered to be one of the least effective air purifiers on the market— likely because it was aesthetically pleasing and had great marketing. They have since been forced to retract their claims and have added a regular HEPA filter to their machines. 5 star reviews are not based on particles, science, or effectiveness. Instead, they’re based on experience, which isn’t super reliable in this area.