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 effect 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 Technologies. 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.

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.

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.

Noise: 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 Cleaner Technologies). 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. 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.

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