 being concise.
Several factors other than the ability of air-cleaning devices to reduce airborne pollutant concentrations should be considered when making decisions about using air cleaners. These include:
Installation. Use, and Need for Maintenance
The air-cleaning unit may have certain installation requirements that must be met, such as an adequate and accessible power supply or the need for access during use, repairs, or maintenance.
After installation, operating and maintenance procedures specified by the manufacturer need to be followed to assure adequate performance from the air cleaner. Filters and sorbents must be cleaned or replaced and plates or charged media of electronic air cleaners must be cleaned, sometimes frequently. To avoid electrical and mechanical hazards, the purchaser should ascertain that the unit is listed with Underwriters Laboratories (UL) or another recognized independent safety testing laboratory.
In addition, during cleaning an effort needs to be made to ensure pollutants do not get reemitted back into the air. For example, when filters are removed, excessive movements or air currents should be avoided to prevent redistribution of particles into the air.
Cost
Cost may also be a consideration. Major costs include the initial purchase of the unit, maintenance costs (i.e., cleaning and/or replacement of filters and other parts), and operating costs (e.g., costs for electricity).
In general, the most effective units (e.g., those with high air flow rates and efficient particle capture systems) are also the most costly. Maintenance costs vary depending on the device, and should be considered before choosing a particular unit. In comparison to purchase and maintenance costs, operating costs for portable units (e.g., costs for electricity) are negligible.
Production or Redispersal of Pollutants
Another consideration is whether some units will produce new pollutants or redisperse old ones. The potential for ion generators and electronic air cleaners to produce ozone, a lung irritant, may be of concern, particularly if electronic air cleaners are not properly installed and maintained.
This requires further study. At least two manufacturers of portable units advertise that their products produce ozone to facilitate removal of harmful gases, but the levels produced by these devices and the possible health effects are not known. Measurable levels of ozone were produced by one portable and two induct electrostatic precipitators in tests by EPA, and the Agency is conducting research to determine if the concentrations produced by the induct air cleaners are potentially harmful.
The Agency recently released the fact sheet, "Ozone Generators That Are Sold As Air Cleaners." The purpose of this document (which is only available via this web site) is to provide accurate information regarding the use of ozone-generating devices in indoor occupied spaces. This information is based on the most credible scientific evidence currently available.
The production of fine particulate material by electronic air cleaners has also been reported. Also, filters and other particulate control devices may remove particles from air and then may reemit gases and odors from the collected particlesl, and materials used in the construction of air cleaners may themselves emit chemicals to indoor air (e.g., formaldehyde may be emitted if particleboard is used in the air cleaner housing).
Inability to Remove Some Odors
A number of air cleaners tested were found to reduce the levels of cigarette smoke particles in the air.
However, the odor of cigarette smoke remained because many of the devices do not contain effective systems to remove the gaseous products of cigarette smoke and because the gaseous products may be adsorbed and later reemitted by articles in the home. To overcome this, some devices scent the air to mask odors, which may lead the occupants of the home to believe that the odor-causing pollutants have been removed.
Possible Effects of Particle Charging
Another factor with respect to ion generators, particularly those that do not trap some of the charged particles, is the effect of particle charging on deposition in the respiratory tract. Experiments have shown a linear increase in particle deposition with charge; therefore, the use of ion generators may not reduce the dose of particles to the lung.
Soiling of Walls and Other Surfaces
Ion generators are generally designed not to remove particles from the air but to deposit them on surfaces around the room. This results in soiling of walls and other surfaces, especially if the particles charged by the apparatus are not collected on a filter.
Noise
Noise may be a problem with air cleaners containing a fan. Some portable units operating at high speed can produce noise equivalent to a small vacuum cleaner or that made by light traffic at 100 ft. Even at low speed, some models produce an annoying hum or whine.
 - excerpt from Residential Air Cleaning Devices: A Summary of Available Information booklet by Office of Air and Radiation (OAR)
Indoor Environments Division (IED)
Washington
- 1990 |
