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How Do They Work? Air Purifiers

Americans spend an estimated $350 million annually on air purifiers for their homes, with asthma and allergy sufferers responsible for most of the sales source.

But scientific studies and testing reveal that many Air Purifiers aren’t effective at all, and some may be causing harm.


The notion of purifying air has merit, however. The air inside the typical home is generally dirtier than the air outside, because a house can be a source of air contaminants.

Moisture can lead to the development of mold and mold spores. Forced-air heating and cooling systems circulate dust particles and bacteria throughout the house.

Pets shed fur and give off dander, while smokers pump toxins into the air. Pollen and other outdoor allergens can blow in through open doors and windows (or through a window or door screen) and become caught in carpet or upholstery.

The end result is that the average house tends to concentrate contaminants in greater quantities than the outdoors. This concentration isn’t usually too harmful for a healthy person, but children and people with allergies and respiratory difficulties can experience ill effects.

Reducing the level of contaminants can help alleviate some of these problems and using an air purifier is one way to do it.

Ionizing Purifiers:

These air purifiers use a method called corona discharge to create charged molecules called ions. Most atoms in the air have a neutral charge — they have the same number of negatively-charged electrons as positively-charged protons.

The corona discharge is a small but intense electrical field. Molecules passing through it will pick up an additional electron, giving the molecule a negative charge, or it may have an electron knocked off of it, giving it a positive charge.

Larger particles in the air, such as dust or other contaminants, are more likely to be ionized because they make larger targets for the electrons as they pass through the corona discharge.

Once a particle is charged, it will be attracted to anything with the opposite charge. Two metal plates within the purifier are charged (one negative, one positive) to attract these particles. Also, particles in the air will be drawn to each other if they have opposite charges. As the particles clump together, they get heavier and eventually they settle out of the air.

Ozone Generators:

An ozone generator works much like an ionizing purifier, but it is designed to alter molecules of oxygen and turn them into ozone, a molecule made up of three oxygen atoms. Oxygen in the atmosphere exists as dioxygen, a molecule made up of two oxygen atoms. When these molecules are exposed to a corona discharge or UV light, some of the dioxygen molecules split into separate oxygen atoms (free oxygen).

While most of this oxygen recombines into dioxygen, some of the atoms form ozone.

Manufacturers of these devices claim that the ozone deodorizes and disinfects the air. Many also claim other health benefits from the presence of ozone. However, there is strong evidence that ozone does not accomplish air purification.

Ozone is also known to be a toxic gas. It is not a very stable molecule — it reacts readily with other chemicals that may be in the air, forming new compounds that can be more dangerous than the ozone itself.

Ozone also oxidizes metals and causes corrosion. The same process that creates ozone also creates nitrogen oxides, leading to further reactions with compounds present in the air and with ozone itself.


Many purifiers incorporate an adsorbent material to take care of odors, fumes and chemicals in the air. Adsorption (not absorption) is the process of one substance being trapped on the surface of another substance. The most common adsorbent is activated charcoal, which is extremely porous and has many microscopic “nooks and crannies” to trap passing molecules.

Larger particles are simply stuck in the many pores in the charcoal. Electrostatic attraction draws some substances into the pores. Certain substances react chemically with the charcoal and bond to it. The high surface area of the charcoal gives it lots of bonding places. The process used to make the charcoal can affect which compounds it is better at adsorbing.

UV Light:

Ultraviolet radiation renders certain micro-organisms sterile (and harmless). Some air purifiers feature a UV light that bathes the air as it passes through, eliminating the potential harm of airborne bacteria and viruses.


Industries often use air purifiers that are far more powerful (and expensive) than consumer models. A company may use them because the manufacturing process requires a contaminant-free environment, or it might pull contaminants out of the air before the factory expels them so it can meet environmental standards.

Some companies use a massive air circulation and filtration system that completely changes over the air in the room 10 times per minute. Other companies use scrubbers, high-density filters, mist collectors and extraction units to decontaminate the air leaving their facilities.

These devices can cost tens of thousands of dollars (a cleanroom facility like Intel’s probably costs millions), so they aren’t suitable for home use.

Terminology and Definitions:

Along with each recommendation, we tried our best to include a brief explanation of the stand out features so that you know what makes each particular device valuable.

For some people, those short details are all they need to make a wise decision, but for others, they may want to know more about what a particular feature means. Below is a list of all of the terminology used on this page regarding air purifiers and their definitions.

Pre-filter – An essential feature of air purifiers that use a HEPA style filter. The pre-filter prolongs the life of the main filter by preventing large particles from damaging it and wearing out the filter faster. Most pre-filters are washable and reusable and last a lifetime.

True HEPA Filter – This is the highest standard air filter you can get for an air purifier. In order to carry this label, the filter must meet strict regulations set by the United States Department of Energy (DOE) and capture at least 99.97% of particles as small as 0.3 microns.

BioGS HEPA Filter – This filter is a more advanced version of the True HEPA filter. It’s specially designed to reduce the build-up of particles on the filter that degrade it over time. If maintained properly, a BioGS HEPA filter can last anywhere between 18 months to 3 years.

HEPA-type Filter – This filter is a lower quality version of a True HEPA filter and doesn’t meet the standards set in place by the U.S. DOE mentioned above. It could capture particles as small as 1 micron, 2 microns, 5 microns or larger. To know for sure, you must read the fine print on the product specifications.

Activated Carbon (or just Carbon) Filter – This filter is very porous and has a large surface area, which gives it the capability to absorb odorous particles and gases. No other filter can remove the smells produced by smoke, pets, cooking, chemicals, mold, etc. as well as this one.

Ion Generator (or Ionizer) – This technology emits negative ions into the air as a way to clean it. Particles like dust, bacteria, and allergens are positively charged and these negative ions form a bond with them. Once bonded, those contaminants become too heavy to stay in the air. Ionizers don’t require filter replacements, because they don’t use them, however, some products do have electrostatic collection plates that collect these fallen particles. Electrostatic collection plates can be washed and reused.

UV-C Light – The UV in UV-C stands for “Ultra Violet.” Ultra Violet light is part of the electromagnetic spectrum that makes up electromagnetic radiation, which includes light, radio waves and x-rays. UV-C is a sub-band of UV light and is a powerful form of radiation that kills microorganisms, but is completely harmless to humans.

Ozone – Ozone is a highly reactive molecule that is known for killing bacteria, viruses and removing odors. However, the same chemical properties that allow it to react with organic material outside of the body is the same thing that can cause it to harm human health. Certain levels of ozone exposure can cause decreased lung function, chest pain, shortness of breath, coughing and irritation of the throat.

Plasma Wave Technology – This technology safely destroys airborne pollutants without causing harmful ozone. As filtered air is leaving the air purifier unit, it passes through a type of electric pulse that creates positive and negative ions. This puts air in a plasma state. Once this plasma combines with water vapour, it forms hydroxyl radicals. Hydroxyls attack pollutants like germs, bacteria, viruses and chemical gases, and once destroyed, the hydroxyls reform into harmless water vapor.

Smart Enabled Features – This allows the air purifier to be controlled by a mobile device using an associated app. Things like schedules and timers can be set up as well as tracking the degradation of the filters. Some apps also include a real-time monitoring of air quality, which lets you see how good or bad the air is inside your home at any given moment.

Clean-Cel Anti-Bacterial Treatment – This treatment prevents the growth of bacteria, mold and fungi on an air filter. This extends the life of the filter and reduces odors caused by these microorganisms.

Smart Sensors – These sensors monitor the air quality within a room and tell the air purifier how to adjust itself in order to eliminate the pollutants. Commons types of smart sensors include ones for dust and odors. When high levels of either of these contaminants are detected, the air purifier will adjust automatically to combat them.

Light Sensor – This sensor monitors the light levels inside a room and when it gets too dark, it triggers the air purifier to go into sleep mode. Sleep mode is a quieter, more energy-efficient operation for night time use.

Electrostatic Collection Plates – See definition for Ion Generator (or Ionizer).

Some FAQ”S—

Do air purifiers really work?

A HEPA filter is a type of mechanical air filter; it works by forcing air through a fine mesh that traps harmful particles such as pollen, pet dander, dust mites, and tobacco smoke. You can find HEPA filters in most air purifiers. These are small, portable units that may work for a single room.

Can air purifiers be harmful?

However, ozone can be extremely harmful. Any good UV filter should actually minimize the amount of ozone in the air. UV air purifiers tend to not be extremely effective, however. Because they can not remove particulate matter, many microorganisms avoid the UV rays due to shielding provided by particles.

Do air purifiers make the room cold?

Air purifiers, by design, do not create cold air. The air that comes out of them is just air that is being circulated from the room. It feels cold due to the fan pushing it. Air purifiers do not have a cooling unit inside them like an air conditioner does that lowers the temperature of the blown air.

Can an air purifier make you sick?

Ozone generator products sold as air purifiers can cause symptoms of sickness and headaches. A HEPA purifier does not add anything to the air in your home, so it can‘t make you sick. HEPA air purifiers actually remove things that make you sick, so they can actually help you stay healthy.

Do I need an air purifier or humidifier?

Air purifiers and humidifiers have different functions. Air purifiers are clean indoor air, but do nothing for indoor humidity levels. They remove dust and smoke from the air, as well as allergenic substances like animal dander and pollen. Humidifiers add water into the air, but do not clean it.

How much electricity does an air purifier use?

Most HEPA purifiers consume around 30-250 watts per hour, depending on the size and model. Hypothetically, if you were to use the purifier for around 24 hours each day for a year, you would be paying around $39 to $328 annually when using a baseline rate of $0.15 per kilowatt hour (kWh).

What is the difference between air purifier and ionizer?

The major difference between an Ionic air purifier vs HEPA air purifier is how each product removes impurities from the air. A HEPA air purifier operates by sucking air into the device through a dense, physical filter that traps airborne contaminants. It then pushes out clean, fresh air into the room.

What are the best air purifiers?

Top 10 Rated Air Purifiers List:



3) Honeywell HPA300 True HEPA Allergen Remover.

4) Winix PlasmaWave 5500-2.


6) Hamilton Beach TrueAir Compact Pet Air Purifier.

7) Winix WAC9500 Ultimate Pet True HEPA Air Cleaner.

8) Dyson Pure Cool Advanced Technology Tower.

9) GermGuardian AC5000E Air Cleaner.

10) Philips 1000 Series AC1215/20 HEPA Filter Air Purifier


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