How Do Air Purifiers Work?

By Mitchell Tollsen
Last Updated On June 17th, 2020

Believe it or not, the air quality inside your home can be 5 times more polluted than the air outside. Indoor pollution can be the result of the following sources: Chemical…

How Do Air Purifiers Work?

Believe it or not, the air quality inside your home can be 5 times more polluted than the air outside. Indoor pollution can be the result of the following sources:

  • Chemical fumes from furniture, flooring, paint, and cleaning products
  • Airborne mold and mildew spores caused by high humidity
  • Dust, pollen, pet dander, and other allergens
  • Dust from forced-air cooling and heating systems
  • Smoke from cooking or indoor fireplaces
  • Emissions from nearby vehicles and urban pollutants
  • Asbestos in the home
  • Radon leaks or other harmful gas leaks

To create energy-efficient homes, we make our living spaces airtight. However, this process decreases ventilation and seals harmful pollutants inside, resulting in poor indoor air quality. Since we spend between 80 and 90 percent of our time breathing indoor air, fine particle contaminants can impact our overall health—this is especially true for asthma and allergy sufferers.

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According to the U.S. Environmental Protection Agency, one of the simplest ways to combat this issue and ensure the air inside the home is safe is by using a high-quality home air purifier.

What is an Air Purifier?

An air purifier is a device that cleans the air of harmful airborne particles such as dust, mold spores, gases, chemicals, and odors. Powerful fans inside the machine draw in air and move it through a series of particle filters. Each filter captures a different type of pollutant. Once the air is clean, the fan expels it back into the environment. This process leaves the air in your home free of harmful bacteria, allergens, and chemicals. The more efficient the machine, the more the air it will be able to clean per hour.

However, not all air purifiers rely on the same technology, nor do they use the same type of filtration system. Some machines may be able to capture tiny particles such as pollen, pet dander, or dust mites, while others may not.

Frequently Asked Questions

What do air purifiers remove from the air?

Depending on the type of filters used in the machine, air purifiers can remove contaminants and toxins from the air.

With an Activated Carbon filter, these machines can remove natural gasses; VOC (Volatile Organic Compounds) emissions from furniture, carpeting, and cleaning products; unpleasant odors; and chemical pollutants.

If the machine also uses a True HEPA air filter, it will be able to remove 99.97 percent of all air pollutants up to 0.3 microns in size. These filters can prevent the spread of bacteria and viruses.

Most modern air purifiers also have a pre-filter. The pre-filter is the first barrier air travels through when it enters the machine. This layer captures larger particles, so the primary filter, typically the HEPA filter, is not bogged down. Instead, the HEPA filter can focus on removing fine particle contaminates. An effective pre-filter will increase the overall efficiency of the air purifier and its extraction rate.

Most modern air purification systems will have a HEPA filter, Activated Carbon filter, and a pre-filter.

What is a micron?

A micron, or micrometer, is one-millionth of a meter and roughly 1/25,000th of an inch. Micrometers are used to measure the size of each airborne particle. These particles are not visible to the naked eye, and they can only be seen with a microscope. Small particles can be inhaled and move quickly throughout the air in your home.

A True HEPA filter can capture particles as small as 0.3 microns in size. Dust particles are roughly 0.3 microns, while bacteria range from 0.2 to 2 microns. So, a high-quality air filter will be able to capture most of these particles.

Are there different types of air purifiers?

There are 5 different types of air purifiers on the market—those that rely on HEPA air filters, activated carbon filters, electrostatic filters, ozone generators, and UV lights. These filter types can be used individually or together in one machine. Below, we outline the 5 most common types of air purification filters.

  • HEPA filters, or High-Efficiency Particulate Air filters, are capable of capturing fine particles up to 0.3 microns in size, this includes pollen, dust mites, dander, and other allergens. These fine particle filters are often made of foam, cotton, or fine mesh and are considered safe and effective. Each HEPA filter will have a MERV rating (Minimum Efficiency Reporting Values). This rating tests the filter’s ability to capture particles between 0.3 and 10 microns. The higher the MERV rating, the smaller the particles it will be able to capture. Most air purifiers will have a HEPA filter with a MERV rating between 7 and 13.
  • Activated carbon filters don’t trap pollutants on their own, so these filters are often paired with other technologies. Carbon filters are effective at trapping chemicals, VOCs, gases, and pet odors.
  • Electrostatic precipitators give a negative charge to incoming oxygen atoms to trap them to an electrostatic plate. However, these plates tend to fill up with particles quickly, requiring constant maintenance. Filter replacement costs with an electrostatic filter can become costly. Additionally, these devices tend to release ozone into the home, which can contribute to further indoor air pollution and health issues.
  • Ozone generators produce ozone to eliminate impurities from the air. This process is often used in water purification. But, to effectively remove indoor air pollution, the machine must produce high levels of ozone, which can be harmful to the lungs.
  • Ultraviolet light air purifiers use a UV lamp to penetrate the cell of microorganisms once it is drawn into the device. This process kills the pollutant and prevents further contamination. Since this technology does not trap the pollutant on its own, it is often paired with other air purification systems, such as those with a HEPA filter.

What is a CADR Rating?

A CADR rating stands for Clean Air Delivery Rate. This rating measures the volume of air (in cubic feet per minute) the machine can clean. Testing measures both fine particulate matter and larger particles. CADR testing is done by using smoke, pollen, and dust since these particles have various micron sizes. Each particle is tested and given a CADR rating.

Home air purifiers with HEPA filters tend to have the highest CADR ratings, between 240 and 180. Those with a 179 to 120 are also suitable. If the rating is lower than 60 for any of the tested particles, the machine may not sufficiently remove the pollutant from the air.

Who should use an air purifier?

Clean air in the home is critical for those who suffer from asthma or allergies. Harmful pollutants can trigger asthma attacks and symptoms of allergies. HEPA filters can remove the majority of these triggers from the air, helping you and your loved one’s breathe easier.

If you live in a busy city with mild pollution levels, you may also want to consider an air purifier. Research shows city dwellers are at a higher risk of developing lung cancer and other respiratory illness. A good air purifier will eliminate outdoor air pollutants from your home and produce cleaner air.

Do air purifiers make the room cold?

Air purifiers do not directly adjust the temperature of the room. However, these machines do have fans that pull air in and force it back out again. The constant movement of air can make a smaller room feel cooler. The more filters the air passes through before being expelled, the slower the airflow will be.

Do air purifiers use a lot of electricity?

The average air purifier consumes 550 kilowatt-hours of electricity per year. This is roughly the same energy use as your computer. To use less power, you can lower the fan speed setting when you are not home.

How long does it take for an air purifier to start working?

When you first turn the air purifier on, it can take anywhere from 30 minutes to 2 hours to clean the air in a standard 219 square foot room. The more efficient the machine, the less time this process will take.

How many hours a day should I run my air purifier?

Running your air purifier for an hour or two each night will not adequately clean the air in your home. These machines are designed for continuous use, so the air inside your house always remains clean. Ideally, this cleaning should take place around the clock.

How Do Air Purifiers Work?

However, if you are concerned about energy efficiency, you can reduce this time to about 12 hours a day. Since most air purification systems extract at a rate of 6 air changes per hour, 12 hours should be sufficient to keep the air inside your home free of toxins. If you choose to leave the machine running 24 hours a day, you can switch to a low setting to save energy.

Can air purifiers be harmful?

Safe and effective air purifiers use a particle filter system to trap and eliminate contaminants. This process produces no harmful byproducts and is healthy for you and your family. True HEPA filters remove harmful pollutants and produce clean, purified air.

However, ozone generators and electrostatic air filters can produce high levels of ozone. Over time, this can lead to respiratory issues.

What is the difference between an air purifier and a humidifier?

Air purifiers are designed to trap fine particles such as dust, dander, mold, and pollen. These machines are not able to change the humidity level in your home.

Humidifiers work to add moisture to the air to increase humidity levels and prevent dryness. Humidifiers do not remove indoor air pollution or reduce the number of fine particles in the air.

How big should my air purifier be?

A desktop or small air purifier should be large enough to clean a small room (between 155 and 219 square feet) sufficiently. However, if you are looking to clean the air in a large space (between 300 to 500 square feet), a taller, slimmer air purification system will be your best bet.

Where should you place an air purifier?

Each air purifier will have an inlet where the air is drawn in and cleaned, and an outlet where fresh air is pushed out. It is best to place the machine in a location where the clean air can circulate freely in the room. It is also helpful to avoid corners and other places where airflow could be obstructed.

Another option is placing the device in the room where you spend the most time or close to potential sources of pollution. If you suffer from allergies that keep you up at night, it may be helpful to place the air purifier in your bedroom during the night.

How often should I change the air filter in my air purifier?

A high-efficiency filter can be replaced every 3 to 6 months depending on usage and filter size. Most air purification systems will let you know when the filter is ready to be changed.

Ozone generators and electrostatic filters may need to be replaced more frequently.

Do air purifiers get rid of germs?

Airborne viruses and bacteria can remain in the air for up to 3 hours after an infected person has coughed or sneezed. Some air purifiers can remove bacteria and viruses from the air in your home. To ensure the device can remove these contaminants, look for the following features.

  • A HEPA filter lined with silver nanoparticles. The silver coating on the filter has antiviral and antibacterial properties that kill the germs in your air. This feature helps to stop the spread of harmful germs naturally. Although most True HEPA filters can trap bacteria up to 0.3 microns in size, some viruses can be as small as 0.1 microns. Therefore, it is best to opt for one with a silver nanoparticle coating.
  • An air purifier with ultraviolet light (VC-C) can also eliminate the bacteria and viruses from the air. These powerful lights destroy the DNA makeup of the pathogen or microorganisms. This process kills the germ, so it is no longer a threat. On its own, ultraviolet light cannot draw in and purify the air. Therefore, UV lamps are often paired with other air purification systems, such as a HEPA filter.
  • Some air purification systems have a ceramic heat chamber. The chamber heats up to 400 degrees Fahrenheit to incinerate bacteria and viruses within the air.

Do air purifiers help with smell?

Air purifiers with a powerful internal fan will naturally improve air circulation and thereby improve odor. However, a True HEPA filter will not wholly absorb and eliminate odor from the air. If the machine has both a HEPA filter and an Activated Carbon filter, it will be able to remove most odors. Carbon filters help to capture small odor-causing particles such as chemical gases, VOCs, and smoke.

How long does an air purifier last?

A high-quality air purifier with a HEPA filter can last up to 5 years if cared for properly. Larger machines that take in more particulate matter may last around 2 to 3 years.

Does every room need an air purifier?

While an air purifier in every room would be helpful, you can save money by placing one only in the rooms you spend the most time in. For example, your home office, bedroom, and living room would be an excellent place to start. For those with allergies, an air purifier in the bedroom can help improve sleep quality.

How much maintenance is required on an air purifier?

Most modern air purification systems require very little maintenance. The filters inside the machine should be changed every 3 to 6 months. Replacement times may vary depending on the size of the room and the frequency of use. If there are multiple filters, such as a HEPA filter, Activated Charcoal filter, or pre-filter, each one will need to be replaced separately.

Are air purifiers loud?

The noise created by an air purifier will depend on the fan speed. Air purification systems with HEPA filters often have a decibel level of around 35dB with a low fan setting and around 70dB with a high fan setting.

For comparison, a modern refrigerator has a dB of 32 to 47, while a tower fan has a dB of around 60. In most cases, this noise level will not disrupt sleep. If you are sensitive to noise during sleep, you can opt for a lower setting at night.

This article is for informational purposes and should not replace advice from your doctor or other medical professional.


About the author

Mitchell Tollsen is a graduate student and a freelance writer who’s contributed to the Early Bird blog for three years. Mitchell’s always been fascinated by the science of sleep and the restorative processes our bodies undergo when at rest. The self-titled “Sleep Expert” is always looking for ways to improve his shut-eye, and throughout the years has implemented numerous lifestyle changes and tried dozens of sleep-promoting gadgets to determine the best ways to truly get better rest.

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