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Portable Room Air Cleaner Buying Guide

Important Features for Portable Air Cleaner Systems

Air Cleaner Technology

When considering the purchase of any air cleaner make sure you understand the technology used by the air cleaner and the potential issues that may be inherent in that technology which could affect the efficiency of the air cleaner and your health. Some technologies release charged particles which deposit on room surface or can be inhaled into the respiratory tract and be difficult to expel. Other technologies release a toxic pollutant called ozone that is hazardous at any indoor level. Many health, state and federal agencies such as the American Lung Association, the US Environmental Protection Agency and the California Air Resources Board publicly condemn the use of ozone emitting devices in the home. Review our information on Air Cleaner Technology below. Mechanical filtration using HEPA technology has been used in critical environments such as hospitals, cleanrooms and lead abatement projects and has proven effectiveness. HEPA filters also help control microorganisms in the indoor air. Microorganisms such as bacteria and viruses are either trapped directly by the HEPA media or captured as the microorganisms are carried in the air by larger particulates. Microorganisms require moisture and a food source to survive, once captured by the HEPA filter these and other microorganisms quickly expire due to being trapped in an unsuitable environment for their existence. Look for air cleaning systems that are properly designed to produce HEPA performance of the air exiting the air cleaner.

Sealed System

Quality air cleaners utilize various advanced air sealing techniques and gaskets around the filter media to assure maximum particle and gaseous chemical capture and efficiency. An unsealed air cleaner system with a high air flow rate and low filter efficiency will not be effective at removing pollutants is a room and will disperse potentially hazardous pollutants back into a space. Air will seek the path of least resistance. As the air filter captures particles on the filter media surface, the resistance to air flow through the filter increases and there is a build-up of internal static pressure. With an unsealed air cleaner system, the increased internal pressure will force contaminated air to bypass the filter media and re-enter the indoor environment. Many air cleaner manufacturers include HEPA filters, but these air cleaners are not sealed and the filters do not have gaskets around them to provide HEPA performance! Look for systems that have sealed construction and gasketed filters.


The level of maintenance required by an air cleaner depends on the design and technology used. Air cleaners that use electrostatic precipitation require constant (at least weekly) cleaning of their collection plates to maintain a level of performance. Air cleaners that use electrostatically charged filter media require frequent filter changes as this type of filter media loses it's efficiency quickly as particles build up on the filter. Most air cleaners that use HEPA technology provide filters with a small amount of filter surface area, requiring frequent filter changes. High maintenance can be costly, time consuming and inconvenient. Look for air cleaners that have a large filter surface area, require infrequent filter changes and have low maintenance requirements.

Particle Capture Efficiency

Many air cleaners claim high efficiencies for their filters, but few air cleaners have high efficiencies for their complete air cleaning system. Some air cleaning technologies have high initial efficiencies, but their efficiencies quickly drop off over time because of the inherent characteristics of the technology. Many companies use a HEPA filter and claim to have HEPA performance when in fact their initial efficiencies may only be 50-80%. These claims are based on the theoretical efficiency of the HEPA filter material and not the clean air produced by the air cleaner. Unfortunately, many of these air cleaners are not sealed systems and use ungasketed or poorly gasketed HEPA filters. Other air cleaners may use  product descriptions such as "HEPA-type", "Microfiltration" or "Removes 99% of All Allergens", but these filters do not meet the industry standard definition of HEPA efficiency. Inferior design prevents most air cleaner systems from reaching true HEPA performance. A certified High Efficiency Particle Arresting filter or HEPA filter can capture 99.97% of particles as small as 0.3 microns (1/83,000 of an inch) and are  95-99% efficient at capturing particles below 0.3 microns. Unlike other filter media that quickly becomes less efficient with use, HEPA filter media becomes more efficient with use and will never fall below the HEPA efficiency standard for the life of the filter. Considering 90% of all particles that are troublesome to our health are below 0.3 microns, it is critical that an air cleaner have HEPA performance. Look for air cleaners with sealed and gasketed systems incorporating certified true HEPA filters.

Gaseous Chemical and Odor Control

Gas and odor control is affected by many variables that includes the type and concentration of the gas pollutant, the room temperature and humidity, the quantity, depth and type of gas and odor control media, the room size and the air flow rate through the gas and odor adsorbing media. The location of the odor adsorbing media relative to the particle filtration media is also important. If the odor adsorbing media is placed first, then particles in the air will cover the porous structure of the odor adsorbing media and reduce its effectiveness at trapping odors. By placing the high efficiency particle filter media first, particles in the air are captured before the air reaches the odor adsorbing media and allows the porous structure of the odor adsorbing media to have maximum effectiveness at capturing gasses. Most air cleaners provide poor gas and odor control primarily due to the lack of adequate gas and odor adsorbing media. Air cleaners that use a powdered carbon impregnated open mesh, either as a prefilter or final filter do not provide adequate adsorption capability to remove contaminants, especially for a long term. These filters lack the necessary quantity, density and depth to provide significant contact time between the pollutant gas and the media to be effective. Chemisorption is another way to effectively remove gases and odors. This is a process of using a substance as an oxidizing agent to chemically break down the gas and remove it from the air. The most common oxidizing substance used for this purpose is Potassium Permanganate, which is usually impregnated on a carrier substrate such as activated alumina. Look for air cleaners with substantial amounts of solid granular or pelletized gas and odor control media that is located after the high efficiency particle filter in the air flow through the air cleaner.

Operating Cost

The operating cost includes any maintenance, such as filter replacements, as well as energy costs to power the device. Many air cleaners use inferior technologies and small filters that require frequent changing. For some companies, this is a profitable situation, first selling an inexpensive air cleaner, then requiring frequent expensive filter changes. Poor quality air cleaners use inexpensive and inefficient fan motors and fan designs that use a significant amount of energy. In some parts of the country where electricity is expensive, this can be a high cost. When purchasing an air cleaner, you must consider the long term cost or "life-cycle" cost of the product. This includes the first cost (purchase cost), the expected life of the air cleaner and the operating cost. Buying a high quality air cleaner may initially cost more, but over the life of using the device, it will cost you less to operate in filter replacements and energy costs and be more effective at removing indoor air pollutants. Look for air cleaners that provide quality construction, large filters with long replacement periods and high efficiency fan motors for low energy use.

Upflow or Downflow Air Exhaust

There has been a debate in the air cleaner business over which direction the clean air should exhaust from the portable air cleaner. Manufacturers that make an upflow design point out that a downflow airstream will blow particulates that have settled on the floor up into the room air. Manufacturers that make downflow designs say the upflow design can make people uncomfortable with the exhaust air continuously blowing on people in a room. You could effectively argue good and bad points for each design. Some portable air cleaners discharge their air through a single outlet. In an upflow design this would be uncomfortable if you are positioned near the air cleaner because of the forceful concentrated air stream.

The reality is that either design is effective if the air cleaner was designed properly. With an air cleaner that has diffused the clean air exhaust through many exhaust ports or a large exhaust distribution area, there will be no discomfort from the air moving into the room. Air being discharged from the bottom of an air cleaner will disrupt particulates that have settled on the floor to make them airborne and will capture these particulates on the incoming air stream. The fact is, anytime you walk into a room, settled particulates on the floor will become airborne anyway and the job of an air cleaner is to remove airborne particulates. Select an air cleaner based on features, benefits and technology. If the air cleaner has a properly diffused exhaust airstream, do not be concerned over an upflow or downflow air exhaust design in your purchasing decision.


It is very important that a room air cleaner operate quietly as well as effectively. An important location for an air cleaner is in the bedroom where we spend a significant amount of time and desire a quiet and healthful environment for a good night's sleep that is free of allergens and air pollutants. A quiet air cleaner means the product will be used continuously and at a speed setting that will clean the air within a room several times per hour without disturbing individuals in a room. A consumer will put a noisy air cleaner on a lower level to reduce noise, but this action will reduce the effectiveness of the air cleaner. Poorly constructed and designed air cleaners can be noisy. Noise is created by the fan and motor itself as well as air moving through the filters and air cleaner. The more air that is moved through the unit, the higher the noise level. Noise can also develop from a poor quality fan and motor. The design of the fan blades may produce noise in the process of pushing air. Motors without ball bearings can make noise due to friction and wear. Some technologies that claim to be quiet and work without a fan are not effective at significantly improving indoor air quality (see Air Cleaning Technologies below). High quality air cleaners are designed to minimize noise. They have solid construction and have a significant size and mass to absorb noise. In addition, quality air cleaners use high efficient motors to reduce noise and large filter sizes that reduce static air pressure noise. Look for air cleaners with a quality efficient motor and fan, large filter sizes and durable construction.

Room Cleaning Capacity

The capacity of an air cleaner depends on factors such as air flow rate and system design. Most air cleaning professionals and allergists recommend at least 2 room air changes per hour (ACH) for effective cleaning under normal conditions. See Room Sizing Chart below. This means an air cleaner must move all the air volume in a room through the device at least 2 times each hour. Air flow rates are expressed in cubic feet of air per minute or "CFM". Some air cleaners on the market mislead consumers with inaccurately stating the air flow rating of their air cleaners. These manufacturers label their devices with "free-flow" or "no-load" only flow rates and not the flow rating of the fan when installed in the air cleaner with filters. When a fan is installed in an air cleaner and pushing against the air resistance of the installed filters, it can lose up to 60% of it's "free flow" rating. The static pressure creates resistance to the fan and motor and the air volume performance drops under the load of this resistance. A 400 cfm "free flow" rated fan may only produce 150 - 160 cfm when installed in an air cleaner. Look for air cleaners that state their actual system air flow rates.


A quality air cleaner incorporates all of the previous important features. Air cleaners are an major investment in indoor air quality and the health of your home environment. It is important that system effectiveness, operation costs and long-life quality construction be considered in the purchase of your air cleaner system. We offer only air cleaning systems that meet all of these quality standards.

    • It produces no pollutants itself such as offgassing, ozone and/or charged particles.
    • It is a sealed and gasketed system to provide overall HEPA cleaning performance.
    • It is designed to maximize the effectiveness of each filter stage.
    • It is has long filter life, low maintenance requirements and is designed for continuous long-life operation.
    • It has high system efficiencies at removing sub-micron particles.
    • It has significant gas and odor removal media when controlling these pollutants is desired .
    • It has low operating costs from long filter replacement periods and low energy consumption.
    • It produces low noise levels with quality components and construction.
    • It has adequate room cleaning capacity to meet your needs.

Air Cleaner Technology

Before purchasing an air cleaner, make sure you understand the technology used by the air cleaner and the potential issues that may be inherent in that technology which could affect the efficiency of the air cleaner and your health. Some technologies are ineffective and actually contribute to poor indoor air quality by releasing contaminants back into the air or releasing toxic chemicals or charged particles that can be trapped in the lungs. Many air cleaners may use multiple technologies in their design.

Electronic Air Cleaners

These units use an electronic field to help trap particles. Some manufacturers refer to ionization as a "High Energy Field" or "Electrical Energy Field". There are primarily two types of electronic air cleaners. If considering this technology, make sure the Air Cleaner has documentation to verify no Ozone is being produced and no charged particles escape the Air Cleaner.

Electronic Ionization

Electrostatic Precipitators - As the air particles pass into the air cleaner, an electronic charge is given to them through a high voltage (also called ionization). The charged particles are then attracted to a series of flat plates or low efficiency filter media with an opposite electrical charge. These units can either operate as fanless (plate type) or with a fan.

Ion Generators - These devices charge particles, but unlike electrostatic precipitators, these units don't remove the particulate matter, they only cause them to accumulate and attach themselves to various surfaces around the room. They claim to be air cleaners by removing suspended particles from the air.


    • Beginning efficiency is low compared to mechanical filtration and rapidly loses efficiency. As the charged plates or filter media collect particles, the electrical attraction diminishes because the surfaces become covered with contaminants. This reduces the ability of the air cleaner to capture more particles.
    • Units that capture particles require high maintenance, weekly cleaning or short filter replacement periods. Plates need to be constantly cleaned to remove particle build-up to maintain efficiency. Filters need to be constantly replaced to keep the static charge.
    • These devices generate ozone which is a known lung irritant. Various state and federal agencies warn that ozone generating devices should not be used in the home. (see Ozonation below).
    • Charged particles that are not captured can re-enter the room where they can build-up and soil the surfaces throughout the room. Ion generators specifically work on the principle of depositing particles on room surfaces.  Additionally, these escaping charged particles can be inhaled into the lungs where they become lodged and difficult to expel. In a study referenced by the US EPA published in Atmospheric Environment, "Control of respirable particles in indoor air with portable air cleaners," experiments have shown a linear increase in particle disposition in the respiratory tract with charging, therefore ion generators may not reduce the dose of particles to the lungs.
    • Captured particles on plate type devices can be blown back out into the room because they are not physically held in place. When the device is turned off, such as when cleaning, the electrical charge is stopped and the contaminants can be re-released into the room or inhaled during movement and maintenance periods.
    • These devices may emit loud arcing noises and the US EPA has reported in a publication "Residential Air Cleaning Devices" that electronic air cleaners have been reported to produce fine particulate material.

Ultraviolet Light

Ultraviolet light (UV) is not visible to the human eye. It refers to the part of the wavelength spectrum below visible violet light and above x-rays and gamma rays. All light is a form of electromagnetic radiation. The distinguishing aspect of UV light is the wavelength which is longer than x-rays but shorter than visible light. This technology is commonly used in a variety of healthcare and water quality applications where the control of microorganisms is desired. There is no reliable documentation to demonstrate UV effectiveness in air cleaner applications. If considering this technology, make sure there is documentation to verify the effectiveness of the Air Cleaner at microbiological control due to the use of UV light.

Ultraviolet Light Chart

    • The effectiveness of ultraviolet light at destroying microorganisms such as bacteria, mold and viruses depends on the intensity of the light and duration of time the UV light is contacting the microorganism. Air travels at tremendous speed through an air cleaner. There is little contact time of the UV light on particles. Additionally, biological contaminants may be covered with particulates in which the UV light will never actually shine on the microorganism to have an effect.
    • Different microorganisms require different light intensities and contact duration to kill them. This is difficult to control in a light chamber where the particles can be at various distances and locations from the UV light source.
    • UV Light gets weaker over time and requires regular maintenance.
    • UV light can degrade the filter media and other components of the air cleaner.
    • The Centers for Disease Control (CDC) states that UV light in hospitals does not add to the effectiveness of HEPA mechanical filtration.

Air Washing

These units consist of an open water holding tank, a fan and a series of plastic disks partially submerged in the water that are turned by a motor. A fan blows air over the wet disks as the disks are turned in the water. The wet surface of these disks release water vapor into the air and also pick up particles in the air from the fan's airstream. These systems are primarily used for room humidification. As an air cleaning system, these units are not recommended.

    • These units are not effective at removing small particles. Some manufacturer's literature indicates removal of particles down to 10 microns. Other product manufacturer's claim lower particle capture when using ionization technology. 90% of all air particles are below 0.3 microns and it is these smallest particles that are potentially the most troublesome to health.
    • The open water holding tank is susceptible to the growth of microorganisms such as mold, bacteria and fungi that could potentially be released into the air along with the water vapor. Manufacturers recommend the use of biocide and fungicide additives to control growth that could potentially be introduced into the air along with the water vapor it is dissolved in.
    • These units require constant maintenance and cleaning. Water has to be added daily, additives to control microorganism growth have to be used continuously and the units have to be completely cleaned every one to two weeks.


Units that incorporate incineration technology claim to clean the air by killing microorganisms. There is a heating element within the unit that reaches temperatures over 400°F. There are no fans, air moves through the unit by the process of convection in which the heated air within the unit rises out of the unit and thereby pulls more air into the unit. Particles within the air carried through the unit are burned at high temperature. This technology is not recommended for effective room air cleaning.

    • These units do not trap particles. They are not a comprehensive solution to clean air. Particles are incinerated at high heat within the unit and are either retained in the unit or they continue in the airflow out of the unit. Burned particles (deadened cell parts) that exit these units can become airborne and then be inhaled into the respiratory tract where they may trigger asthma and allergy symptoms.
    • There is very little air flow through these devices because of the limited nature of natural convection air flow. The manufacturer's stated information indicates about 8 cfm of air movement. Since these units work through contact with particles carried in the air through the unit, low air flow means low contact with pollutants.
    • These devices can get hot. Manufacturer's information indicates temperatures can reach 144°F in the top center of the device. It takes 2 seconds to produce a 1st degree burn at 140°F and 5 seconds to produce second to third degree burns.
    • Effectiveness testing of these units are difficult. Microorganisms are affected by numerous factors and vary up and down constantly depending on changes in the local environment. Testing is done with out comparison to other technologies under the same test conditions. Without comparison testing of several technologies under the same test conditions, you can not effectively state a device is best at controlling microorganisms.
    • Long term effectiveness may be an issue and the build-up of incinerated particles within the devices. These devices have a limited lifespan and wear out. No information is provided on product effectiveness over several years. These devices are not user serviceable for maintenance and can not be opened. According to the instruction manual, the lifespan of these devices is 5 years. After which you must throw your $300 product away!

Charged Media Filtration

Many air cleaner manufacturers inappropriately use the word HEPA in their description of air filters that do not meet the industry standard for HEPA efficiency of the filter. This is most commonly seen in charged media type filters. The less dense meshwork of synthetic fibers of these filters have been given an electrostatic charge during manufacture. It is this electrostatic charge that helps to attract particles. They may be used alone or in combination with another technology like ionization.

    • Efficiency level is helped significantly by the electrostatic charge of the filter fibers. As the charged fibers of the filter media collect particles, the electrical attraction diminishes because the surfaces become covered with contaminants. This reduces the ability of the air cleaner to capture more particles.
    • Short filter replacement periods are necessary to keep filter efficiency high. This can be a high maintenance cost. This filter material is less dense than a true HEPA filter, so particle escape becomes a major concern.

HEPA Mechanical Filtration

HEPA Filtration MediaThese units are the best for capturing particulate matter. They utilize a filter media with very high efficiency ratings. We can see to about 10 microns (one micron is 1/25,000 of an inch).  A High Efficiency Particle Arresting filter or HEPA filter can capture 99.97% of particles as small as 0.3 microns (1/83,000 of an inch or 0.00012). A HEPA filter also captures particles below 0.3 microns and can be 95%-99% effective at capturing particles below 0.3 microns in size. These filters were originally designed to trap microscopic particles such as radioactive dust in atomic plants and are commonly used for critical environments like hospitals, clean rooms and lead paint/dust abatement projects.

It is necessary that an air cleaner be a sealed and gasketed system to take advantage of the HEPA efficiency at removing particles from the air. Critical design details are important in achieving high air cleaning performance. If an air cleaner using a HEPA filter is not properly designed, air will bypass the filter as static pressure pushes against the filter and allow particle escape. Most air cleaners on the market include HEPA filters as a sales and marketing tactic, but fail to achieve HEPA performance. You won't find HEPA performance air cleaners at the local mass merchandise store. Sealed and gasketed air cleaners with system efficiencies of HEPA performance are recommended.

HEPA Filtration Micron Chart

    • Unlike other filter media that becomes less efficient with use, HEPA filter media becomes more efficient with use and will trap smaller and more particles as the filter captures more and more particles that fill up the microscopic spaces on the filter fabric.
    • HEPA filtration will remove particles smaller than 0.3 microns at up to 99% efficiency. Combined with high air flow rates, a high performance HEPA air cleaning system has been shown to capture more sub-micron particles such as viruses, bacteria, allergen and tobacco smoke than any other air cleaning technology.
    • Many air cleaners claim to destroy microorganisms, but have never compared themselves directly with HEPA technology. HEPA filtration will not re-release trapped particles back into the air. Microorganisms require a food source and moisture to survive and many microorganisms have limited lifespans. HEPA filters do not provide a food source or moisture for microorganisms to continue to live and therefore they will be killed off while trapped in a HEPA performance air cleaner.


Some air cleaning units produce ozone, a molecule with three atoms of oxygen, either directly or as a by product of ionization and electrical precipitation. High voltage causes the oxygen molecules in the air to create ozone (O3). Ozone does not trap particles, but is claimed to remove odors in the air. Manufacturers of air cleaner systems that produce ozone may refer to the ozone as "Supercharged Oxygen", "Activated Oxygen" or "Enhanced Oxygen" and that they produce clean air in a similar way to a lightning storm. Other claims of producing only good ozone vs. bad ozone in the atmosphere are incorrect. All ozone is the same. On the basis that ozone generators produce an indoor pollutant, there are no safe and acceptable levels of ozone, ozone can interact with the air to create more indoor pollutants and ozone does not remove pollutants or particulate matter, these devices are not recommended.

    • Units that produce ozone only do not remove particulates from the air. They are not a comprehensive air cleaning solution.
    • Ozone itself is an indoor air pollutant and is considered an irritant to the lungs by many health, state and federal agencies. The American Lung Association, the US Environmental Protection Agency and the California Air Resources Board have all publicly condemned the use of ozone emitting air cleaning devices for use in the home.
    • The Centers for Disease Control in Atlanta, GA states "Ozone is an extraordinarily dangerous pollutant....ozone is nearly as effective at destroying lungs as mustard gas". The US Environmental Protection Agency (EPA) has stated that ozone is a toxic gas with vastly different chemical properties than oxygen and when ozone is inhaled, it can damage the lungs. The EPA further states that ozone in low amounts can cause chest pain, coughing, shortness of breath and throat irritation.
    • Scientific evidence demonstrates that ozone released into the air at concentrations that do not exceed public health standards, will not effectively remove viruses, bacteria, molds and many odor-causing chemicals and is therefore generally ineffective in controlling indoor air pollution. Ozone deadens the sense of smell making it difficult to detect odors.
    • Most of these units can not adjust the production of ozone they produce and many factors affect ozone concentrations in a room such as the room size, materials in the room that react with the ozone and the amount of ventilation. Even when using these devices as directed, you do not know if you creating a dangerously high amount of this pollutant in your indoor environment. Generally, an ozone generator will create ozone levels in a home that exceed a Stage 1 Smog alert standard for outside air quality.
    • Ozone emitted indoors can lead to significant increases in indoor levels of other pollutants such as formaldehyde (a suspected carcinogen), other aldehydes, V.O.C.'s an ultrafine particulate matter.


Used primarily for the removal of gaseous contaminants, this is a process of shining ultraviolet light (UV) onto a catalytic surface composed of a titanium oxide (TiO2) surface coating, to create a chemical reaction that converts gases that pass through the device into less harmful substances such as carbon dioxide and water. Claims of odor removal and germicidal properties are also made for this technology. The claims for pollutant control come from limited laboratory setting tests. This technology has not been tested in a working portable air cleaner under real living conditions to adequately prove its effectiveness. If considering this technology, make sure the Air Cleaner has documentation to verify the Air Cleaner has measurable performance for claims associated with Photocatalysis.

    • Units that utilize photocatalysis may produce ozone.
    • Test reports on the technology to reduce V.O.C.'s, utilize a testing chamber with 0.2 cfm air flow rate and contact time of 10 seconds. Testing chamber was 0.14 cubic feet in size. Test conditions demonstrated a 2 - 40 minutes timeframe to reduce contaminant levels by 50%. Available Portable Room Air Cleaners using photocatalysis technology use a fan that moves air over a catalyst coated light tube. The Air Cleaner would produce significant air flow (50-150cfm?), have much shorter contact times and be located in a room of significantly larger volume (over 1,000 cubic feet). Additionally, it is unknown at what distance the gas has to be from the light tube to be affected by the photocatalytic reaction. The actual use of this technology in real life scenarios are substantially different than the test conditions and makes the application's claimed effectiveness at microbial, gas and odor control questionable.
    • Testing for bacterial destruction has similar flaws. Testing was performed with an incubated bacterial membrane exposed to UV-A light to activate the photocatalyst on the membrane for a period of 3-24 minutes. A real life scenario is a photocatalysis Air Cleaner that is pushing air across a light source with a contact time of milliseconds. This does not resemble a similar scenario as the test environment. Even the manufacturer of a photocatalysis device states "New standard tests are needed that use airborne microbes to determine the Germicidal Rate for a photo-catalytic system employing forced air convection. Both airflow and air recirculation would influence the System Germicidal Rate."


This is the physical process of binding gas molecules to a large surface or pores of an adsorbent medium. Activated carbon is the most common media used for adsorption and is produced by heating carbonaceous substances (containing carbon and derived from organic substances such as bituminous coal, wood or coconut shell) to form a carbonized char, then activating (oxidizing) with gases such as steam and carbon dioxide to form pores and creating a highly porous adsorbent material. Zeolites are another type of adsorbent and are a class of naturally occurring minerals derived from volcanic ash. Zeolites can also be reproduced synthetically because of their consistent and predictable porous structure. Adsorption technology is recommended for gas and odor control.

The effectiveness of odor removing media is related to the amount and type of gasses present in the air, the quantity, type and depth of the adsorbent material and the velocity of the air traveling through the media. The location of the odor adsorbing media relative to the particle filtration media is also important. If the odor adsorbing media is placed first, then particles in the air will cover the porous structure of the odor adsorbing media and reduce its effectiveness at trapping odors. By placing the high efficiency particle filter media first, particles in the air are captured before the air reaches the odor adsorbing media and allows the porous structure of the odor adsorbing media to have maximum effectiveness at capturing gasses. Air cleaning devices with carbon powder impregnated on mesh filters do not have the depth and quantity of gas adsorbing media to provide significant odor removing performance for a substantial time period. Room conditions such as air temperature and humidity also effect the capacity of adsorbents to remove odors.

Activated Charcoal Pellets

Activated Carbon Detail View

Activated Carbon Pellets

Close-Up of Activated Carbon Pores


    • Activated carbon has incredible porosity and a large and a highly active surface area. One pound of activated carbon has the surface area equal to 125 acres. Activated carbon is best suited to remove compounds with high molecular weight such as volatile organic compounds (V.O.C.'s) like benzene, toulene and xylene.
    • One pound of Zeolite can have 20 to 30 acres of surface area. These minerals are effective at removing V.O.C.'s and ammonia compound odors such as pet odors from urine. Like carbon, gasses are trapped in the voids of the porous Zeolite structure.


Chemisorbents work through a two step process, first physically binding gasses to a carrier media then, through an oxidative process, the trapped gas molecules are chemically broken down. The common carrier media is activated alumina, which is made by treating aluminum ore so it becomes porous and highly adsorptive. Another carrier media for chemisorption is activated carbon. A binder such as activated alumina is impregnated with Potassium Permanganate to create a chemically active media. Potassium Permanganate is a dark purple substance that is a powerful oxidizing agent. Use of chemisorption for gas and odor control is recommended.

Pelletized Activated Carbon and Activated Alumina with Potassium Permanganate

Pelletized Activated Carbon and Activated Alumina with Potassium Permanganate

    • These odor control substances are best for the removal of high molecular weight gasses such as formaldehyde, ammonia and hydrogen sulfide.
    • This non-toxic media first physically traps selected gas molecules and then chemically destroys them through a process called oxidation. This oxidation process is media based and no oxygen or ozone is generated.
    • Since there is a chemical process involved to break down the odor and gasses, there is no re-emission possible for the gaseous pollutants.

Room Air Cleaner Capacities and Sizing

Determine the size of your room by measuring how wide and how long it is. Multiply the width x length and this is the total square feet of the room space. To find the volume of the room, multiply the floor space by the room height. To compare room volume to air cleaner capacities, determine the number of air changes per hour (ACH) you desire. Indoor air quality professionals and Allergists recommend at least 2 room air changes per hour, designated as 2 ACH. Spaces with high pollutants may require higher air changes to reduce pollutant levels.

To determine how much air must be moved through the air cleaner to provide 2 ACH, you take the total volume of the room and multiply by 2. Air cleaners provide air flow performance in cubic feet per minute, so you must take your total volume of air for 2 ACH and divide by 60 minutes to get a value for cubic feet per minute (CFM).

Note: The location of an air cleaner in a room can effect performance. Try to place the unit in a central location that allows the greatest degree of unobstructed air flow around the air cleaner.

Air Cleaner Room Sizing

Air Cleaner Sizing Example

Room Size
12' x 20' = 240 square feet of floor space (sq. ft.).
Ceiling Height is 8'
240 sq.ft. x 8' = 1920 cubic feet of air volume (cu. ft.).
Two Room Air Changes per Hour
1920 cu. ft. x 2 = 3840 cu. ft. per hour (60 minutes).
Volume per Minute
3840 ÷ 60 = 64 cubic feet per minute (cfm).

In the previous example, an air cleaner must provide a system flow rate of 64 cubic feet per minute of filtered air to clean all the air in a room two times per hour.

Note: Some air cleaner manufacturers provide air flow performance ratings when the fan and motor are under no load or not in the system. Air cleaner system air flow rates can diminish up to 60% of the no load air volume when the filter media is installed due to the resistance to the air flow through the filter media. Please consider this air flow rate reduction when sizing air cleaners with untested system air flow rates.

Room Size and Flow Rate Requirement Chart
(based on 8' ceiling height)

Room Size

Flow Rate to Achieve 2 ACH*

Flow Rate to Achieve 3 ACH*

Flow Rate to Achieve 4 ACH*

75 sq. ft.

20 cfm

30 cfm

40 cfm

100 sq. ft.

27 cfm

40 cfm

53 cfm

125 sq. ft.

33 cfm

50 cfm

67 cfm

150 sq. ft.

40 cfm

60 cfm

80 cfm

175 sq. ft.

47 cfm

70 cfm

93 cfm

200 sq. ft.

53 cfm

80 cfm

107 cfm

225 sq. ft.

60 cfm

90 cfm

120 cfm

250 sq. ft.

67 cfm

100 cfm

133 cfm

275 sq. ft.

73 cfm

110 cfm

147 cfm

300 sq. ft.

80 cfm

120 cfm

160 cfm

325 sq. ft.

87 cfm

130 cfm

173 cfm

350 sq. ft.

93 cfm

140 cfm

187 cfm

375 sq. ft.

100 cfm

150 cfm

200 cfm

400 sq. ft.

107 cfm

160 cfm

213 cfm

425 sq. ft.

113 cfm

170 cfm

227 cfm

450 sq. ft.

120 cfm

180 cfm

240 cfm

475 sq. ft.

127 cfm

190 cfm

253 cfm

500 sq. ft.

133 cfm

200 cfm

267 cfm

525 sq. ft.

140 cfm

210 cfm

280 cfm

550 sq. ft.

147 cfm

220 cfm

293 cfm

575 sq. ft.

153 cfm

230 cfm


600 sq. ft.

160 cfm

240 cfm


625 sq. ft.

167 cfm

250 cfm


650 sq. ft.

173 cfm

260 cfm


675 sq. ft.

180 cfm

270 cfm


700 sq. ft.

187 cfm

280 cfm


725 sq. ft.

193 cfm

290 cfm


750 sq. ft.

200 cfm

300 cfm


775 sq. ft.

207 cfm



800 sq. ft.

213 cfm



825 sq. ft.

220 cfm



850 sq. ft.

227 cfm



875 sq. ft.

233 cfm



900 sq. ft.

240 cfm



925 sq. ft.

247 cfm



950 sq. ft.

253 cfm



975 sq. ft.

260 cfm



1000 sq. ft.

267 cfm



1025 sq. ft.

273 cfm



1050 sq. ft.

280 cfm



1075 sq. ft.

287 cfm



1100 sq. ft.

293 cfm



1125 sq. ft.

300 cfm



*ACH = Air Changes per Hour. A term to represent how many times all the air in a room could pass through an air cleaner in an hour.