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Air Purifiers | Can They Make You Sick?

Air purifiers are a great tool for helping to maintain the best indoor air quality possible—that’s what they are supposed to do, anyway. In reality, any type of technology comes with risks, so it’s important to consider the potential dangers of using air purifiers in our homes and offices.

There are five main types of air purifiers, and they all come with different mechanisms and risks that we will examine in this article.


UV germicidal irradiation purifiers, ionizers, and ozone generators release ozone. This is only harmful at higher levels, but the presence of ozone means there is a risk to health. HEPA and activated charcoal filters are unlikely to cause illness, but they don’t stop all pollutants.

Main Types of Air Purifiers

In this article, we will cover the following prevalent types of air purifiers:

  1. UV Germicidal Irradiation (biological purification)
  2. HEPA Filters (mechanical purification)
  3. Activated Carbon (chemical purification)
  4. Ionizers (photocatalytic purification)
  5. Ozone Generators (chemical purification)

UVGI Air Purifiers

How Do They Work?

UV germicidal irradiation air purifiers are devices mounted high up on the wall of a room. They work by emitting UV rays, creating disinfection zones. Harmful particles are killed by the energy of these UV rays as they pass through the disinfection zone.

The UV rays might not reach into every corner of the room. However, with a good method of circulating the air, such as a fan or an air circulator, you increase the chance that all the air in a room will pass through this zone at some point.

According to the CDC, the rate of particle disinfection is similar to the rate of air recycling in any given space.

These devices are typically used in buildings without HVAC systems, and in places where there is a high risk for the spread of diseases, such as medical facilities or child care centers.

Can They Make You Sick?

The biggest risk of using air purifiers that utilize UV rays is ozone emission. Not only do the UV rays destroy harmful particulates, but they also cause regular oxygen molecules to split into individual oxygen atoms.

two blue uv light

In its singular atomic state, oxygen is not very stable, so it will always try to bind with other atoms and molecules. When they bind to other oxygen atoms, harmless, diatomic oxygen is reformed.

When they bind to already established oxygen molecules, the potentially toxic, triatomic oxygen molecule—better known as ozone—is formed.

Ozone also occurs naturally in our atmosphere; after all, the sun itself emits tons of UV rays. It’s only when it reaches high concentrations that it becomes particularly harmful.

Some common symptoms of ozone over-exposure include headache, dry throat and cough, trouble breathing, and fluid in the lungs. In addition, long-term exposure can lead to the development of asthma.

The United States Environmental Protection Agency has designated 0.05 parts per million as the baseline for a safe level of ozone in breathing air.

HEPA Filters

How Do They Work?

HEPA filters are filters that are installed within the HVAC duct system of a building and that are made from what are, essentially, tangles of fibers. These mechanically block particles from passing through the filter, thus ridding the air of unwanted particles.

There are three filtering mechanisms:

  1. Diffusion: This is the process that targets the smallest particles. These particles are always in random motion in the air and diffusion relies on this random motion to “bounce” the small particles into the filter fibers, which trap them.
  2. Interception: This is effective for mid-sized particles. These travel with the airflow around the fibers but when they get close enough to the individual fibers, they end up sticking to them.
  3. Impaction: This is experienced by larger pollutants and it is probably the one you thought of when we mentioned a filter. These pollutants are too large to fit between or around the fibers, impacting them instead, and not traveling any further.

Can They Make You Sick?

Although HEPA filters do work to remove some particles from the air, there are a few things that they can’t filter out. Volatile organic compounds (VOCs), odors, viruses, and bacteria are all too small to be stopped by a HEPA filter.

As the HEPA filter cannot stop these substances, you are still at risk from them. So, in this case, the HEPA filter doesn’t make you sick, but it also doesn’t protect you.

While mold spores will be removed from the air with a HEPA filter, they will start to accumulate on the filter and become a larger growth of mold. This can end up putting more mold spores into the air than were there originally. In this way, these filters can make you sick.

There is also some controversy over whether or not the fibers that make up a HEPA filter can make their way into the air and cause damage to the respiratory tract.

Activated Carbon Filters

How Do They Work?

Activated carbon filters are also placed in the home’s HVAC system and they also provide filtration. However, they differ from HEPA filters in that they rely on chemical as opposed to mechanical filtration.

The device is made up of a sheet of activated carbon surrounded by mesh fabric. Activated carbon has a very large surface area, which is how this device is so effective.

Activated carbon has many small spaces and holes in between its molecules, which allows air and pollutants to pass through the filter. Now, you might think that this is contrary to the point of a filter, but that’s because you are still thinking of mechanical filtration.

As air particles pass through the filter, harmful ones become trapped within the layers of activated carbon. By trapped, I mean chemically bound to the carbon and, thus, chemically altered.

Carbon is a great inactivator of harmful and/or unpleasant gases. That’s why people suffering from bloat can find relief from taking activated charcoal and people who have taken an accidental overdose of certain medicines are prescribed activated charcoal.

activated carbon charcoal filter and hepa filter

Can They Make You Sick?

Activated charcoal filters do not make you sick as they do not release anything into the air you are breathing. However, they may be ineffective in protecting you from sickness associated with airborne pollutants.

Activated carbon filters work for things like volatile organic compounds and odors. However, they do not work on particles such as dust and pollen.

So, for people who are allergic to pollen, these devices won’t stop them from becoming sick as a result of exposure to allergens.

Furthermore, they can become saturated, in which case they will cease to be effective against even VOCs and odors.

Ionizing Air Purifiers

How Do They Work?

Ionizing air purifiers are located in the ducts of the home. They work by ionization, which is the process whereby a substance is given a charge.

Regular ionizers use a high-voltage current to ionize air molecules. Don’t forget that a current is a flow of electrons from a negative terminal to a positive terminal. These electrons are used to confer a charge on the surrounding air molecules.

There are variations of ionizers, such as the Reme Halo, which is a photohydroionizer. This uses the energy of UV light striking a catalytic target to release electrons from that surface (metal or a ceramic hybrid).

Latest Model RGF Reme Halo (24 Volt) In-Duct Air Purifier System IAQ Ionizer (Reme-H)

Ionized air molecules, specifically negatively charged hydroperoxides, are able to bind to microbial pollutants, interfering with their cell structure and destroying them.

They also confer a charge to pollutants like allergens, causing them to clump together. The larger agglomerates are better filtered out by the HEPA filters in your HVAC system. With increased size comes increased weight. Settled particles are much easier to clean up than airborne ones.

Can They Make You Sick?

There is some evidence that ionizers release ozone, but it depends on the brand, type, and specific mechanisms used by the ionizing air purifier. For example, the Reme Halo produces ozone, but the Reme Halo LED, which is also a photohydroionizer, does not.

RGF REME Halo LED Whole Home in-Duct Kit with Air Switch

As mentioned before, exposure to high enough levels of ozone can pose many health risks, such as flu- and respiratory-related symptoms.

Ozone Generators

How Do They Work?

Ozone generators are used outside of the ducts and are not meant for use without someone present in the room. They use two different methods to generate ozone gas.

The first method is called corona discharge. This occurs when an electrical storm is simulated in order to produce large amounts of voltage, which, in turn, produces relatively large amounts of ozone.

corona discharge in plasma ball

The second method uses UV light to perpetuate ozone production (similar to the incidental effects of photoelectric ionization). Some wavelengths of UV light possess the power to break oxygen molecules apart, leaving them free to bind with other oxygen molecules and form ozone.

Up until now, I have only spoken about how ozone is dangerous to health at certain concentrations. However, ozone itself is actually an air purifier. That fresh, clean air smell that comes with a lightning storm is actually the smell of ozone.

Ozone gas is very reactive and does a good job at reacting with and destroying organic-based particles. This is because as it comes into contact with particles, it oxidizes them. That is, it reacts with the particles to make a new, harmless substance.

Ozone generators are less recommended for constant domestic use and are better suited to deliberate and sporadic air decontamination.

In other words, they shouldn’t be run continuously while you are in the house, but rather treated like a fumigant. You clear the room, run the ozone generator, turn it off, and air the room before occupying it again.

Can They Make You Sick?

Ozone generators are considered to be dangerous and definitely capable of making a person sick.

Ozone is a known toxin (at certain levels) and controlling the amounts generated by these machines is not always possible to the desired extent.

All the effects that ozone has on pollutants can also be exerted within our bodies. As destruction is the outcome, this is clearly not good. Because the ozone enters the body via inhalation, this makes our respiratory system most affected, hence all the respiratory-related symptoms.

Sources

https://www.cdc.gov/coronavirus/2019-ncov/community/ventilation/UVGI.html

https://www.cdc.gov/niosh/topics/ozone/default.html#:~:text=Exposure%20to%20ozone%20may%20cause%20headaches%2C%20coughing%2C%20dry,Workers%20may%20be%20harmed%20from%20exposure%20to%20ozone.

https://molekule.science/pros-cons-hepa-filter/

https://hvactrainingshop.com/activated-carbon-air-filters/#:~:text=What%20is%20an%20activated%20carbon%20filter%3F%20An%20activated,These%20filters%20remove%20gaseous%20compounds%20from%20the%20air.

https://healthfully.com/health-effects-of-ionizers-6693718.html

https://breathebetterair.org/all-post/how-ozone-purifiers-work/

https://en.wikipedia.org/wiki/HEPA

https://en.wikipedia.org/wiki/Air_ioniser

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