Most people buy air purifiers to ease asthma or allergies. In fact these are often recommended by health care professionals. Since allergies are triggered by airborne particles, it is natural to assume that air purification devices will help alleviate the symptoms since they constantly filter contaminants from the immediate environment. While this concept is true to a degree, and despite product claims, there is little definitive medical evidence that these devices help to relieve respiratory symptoms and their use should be individualized. Here is some information that may be helpful to you. It is important to note first that to reduce the contaminants that lower air quality in the home, the Environmental Protection Agency’s (EPA) leading recommendation is to minimize or eliminate the sources of the indoor pollution and to increase ventilation in order to replace bad air with good. However, there are limitations to how much of each of these you can effectively do.
An air purifier is a device which removes contaminants from the air. Air purifiers are manufactured as either small stand-alone units or larger units that can be affixed to an air handler unit. Several different processes of varying effectiveness can be used to purify air and different processes may remove different contaminants.
Filter-based purification traps airborne particles by size exclusion. Air is forced through a filter and particles are physically captured by the filter. This is probably the most common form of air purifier. So called HEPA (High Efficiency Particulate Air) filters were designed in the 1940s, though it was not until the 1950s that they began to enjoy widespread commercial use. Since then, there have been advances which have improved upon the original HEPA filters, but their basic design and function has remained the same for over half a century. HEPA filters remove at least 99.97% of 0.3-micrometer particles (about 1 millionth of an inch), and are usually effective down to 0.01 micrometers in many cases. HEPA filters do not generate ozone or harmful byproducts. According to the EPA, HEPA filters are the most effective filter commonly found in mechanical air cleaners. In a dusty environment it may be valuable to use an easily cleaned conventional filter (prefilter) which removes coarser impurities followed by the HEPA so that the HEPA filter needs cleaning or replacing less frequently. Activated Carbon is a porous material that can adsorb volatile chemicals, but does not remove larger particles. With the adsorption process it may be difficult to completely remove contaminants. Activated carbon is merely a process of changing contaminants from a gaseous phase to a solid phase, and when aggravated or disturbed contaminants can be regenerated in indoor air sources. It is normally used in conjunction with other filter technology, especially with HEPA (Hybrid Filter). Other materials can also absorb chemicals, but at higher cost. Ionizer Purifiers use charged electrical surfaces or needles to generate electrically charged air or gas ions. These Ions attach to airborne particles which are then electrostatically attracted to a charged collector plate. This mechanism produces trace amounts of ozone and other oxidants as by-products. There are two major subdivisions: the fanless ionizer and fan-based ionizer. Fanless ionizers are noiseless and use little power, but are less efficient at air purification. Fan-based ionizers clean and distribute air much faster. Ultraviolet germicidal irradiation – UVGI can be used to sterilize air that passes UV lamps via forced air. Air purification UVGI systems can be freestanding units with shielded UV lamps that use a fan to force air past the UV light. Other systems are installed in forced air systems so that the circulation for the premises moves micro-organisms past the lamps.
The Effectiveness of Air Cleaners
The main function of most air cleaners is to remove smaller contaminating particles. Research has shown that good air cleaners, even those of the smaller, portable variety, are up to 90% effective in reducing these smaller particles. The EPA has certain recommendations regarding the use of portable air filters. In order to achieve maximum effectiveness, the portable air cleaner should be placed somewhere away from walls or other obstructions and positioned in such a way that the clean air is blown into open, occupied areas. If there is some specific source of pollution, the purifier should be placed nearby. Such purifiers work far better when all doors and windows of the room in which they are located are closed.
Do Air Purifiers Work For Mold Removal?
Partially. Some air purifiers may effectively remove mold particles from the air but are ineffective against killing mold spores. Spores are typically resistant even to UV light treatment. However, if spores become trapped in a filter, this does keep them from proliferating in your home. Careful and proper disposal of used filters is essential. We recommend changing filters outside your home to prevent unwanted release of trapped particles and spores.
Do Air Purifiers Work For Pet Allergies?
Partially. Some air purifiers can remove pet hair and dander trapped in the air. However, heavier pet dander particles often fall out of the air column and settle onto surfaces. Frequent cleaning is recommended. Ideally, you should keep pets out of the bedroom area to avoid contact with pet dander throughout the night and other sleeping times.
Do Air Purifiers Help With Allergic Rhinitis (Hay Fever)?
Hay fever can be caused by various pollens, fungi and mold spores, dust mites or cockroaches, and pet dander. Air purifiers range in their effectiveness of cleaning the air of these particles depending on model type. Air purifiers are most effective at reducing pollen particles in the air column. Most allergens however are typically heavier particles that fall out of the air column and must be cleaned from surfaces. Remember to use allergen covers on bedding and pillows to protect against the most common exposure to dust mites. Keep pets out of sleeping areas. Use HEPA filter equipped vacuums to clean surfaces.
Limitations of HEPA Filters
Even the most advanced residential air purifications systems cannot eliminate all airborne contaminants, especially ones released by contact with items such as pillows, rugs and furniture. The particles have to pass through the mechanism before they can be removed, and it can take even the best air purifier 15-20 minutes to clean the air in typical room depending on the fan speed of the unit. HEPA filters only target airborne particles, not gasses. Although this means that a HEPA filter will help clean the air of many common pollutants, it also means that many others will pass right through the filter undisturbed. Also with respects to airborne particles, the relatively larger ones are often missed by the air cleaner because gravity pulls them to the ground more quickly than smaller particles, keeping them out of the purifier’s reach. Therefore, no one should ever expect air cleaners alone to have a significant impact on indoor air quality. Though there are limits to the effectiveness of HEPA filters they may be preferable to the so-called “HEPA-type” filters that are commonly found in lower-end small air cleaners, simply because HEPA filters must meet certain standards to be called HEPA, while “HEPA-type” could mean nearly anything. HEPA filters typically are more expensive than other filters. Filters of any type will almost always need to be regularly replaced at least once or twice a year, as well, meaning that there is an extra recurring cost in addition to the initial price of the purifier.
Remember, air cleaners are not meant to be a substitute for the other methods of cleaning your home’s air.
Other Air Purifier Feature Considerations
Once you have determined the correct type of air purification system that works best for you, you also need to consider the following factors before purchasing:
A Humidifier is a household appliance that is designed to increase humidity (moisture). Though humidifiers have been touted to prevent headaches, dry skin, coughing, sneezing, itchy eyes, cracked lips, and respiratory problems these claims may not be true for all users. There are point-of-use humidifiers, which are commonly used to humidify a single room, and whole-house or furnace humidifiers, which connect to a home’s HVAC system to provide humidity to the entire house.
Evaporative humidifiers - The most common humidifier, an “evaporative”, “cool mist”, or “wick humidifier”, consists of just a few basic parts: a reservoir, wick and fan. The wick is a filter that absorbs water from the reservoir and provides a larger surface area for it to evaporate from. The fan is adjacent to the wick and blows air onto the wick to aid in the evaporation of the water. Evaporation from the wick is dependent on the relative humidity. A room with low humidity (drier) will have a higher evaporation rate compared to a room with high humidity. Therefore, this type of humidifier is self-regulating: As the humidity of the room increases, the water vapor output naturally decreases. These wicks become moldy if they are not dried out completely between fillings, and become filled with mineral deposits over time. They regularly need rinsing or replacement. If this does not happen, air cannot pass through them, and the humidifier stops humidifying the area it is in and the water in the tank remains at the same level. Also called a “cool mist humidifier” the Impeller humidifier actually throws out tiny drops of water into the air via a rotating disk.
Vaporizer – This is also known as a Steam Humidifier or a Warm Mist Humidifier. This unit boils water, releasing steam and moisture into the air. A medicated inhalant can also be added to the steam vapor. Vaporizers may be more healthful than cool mist types of humidifiers because steam is less likely to convey mineral impurities or microorganisms from the standing water in the reservoir.
Ultrasonic Humidifier – A metal diaphragm vibrating at an ultrasonic frequency creates water droplets that silently exit the humidifier in the form of a cool fog. This is an extremely fine mist, about one micron in diameter that is quickly absorbed into the air flow. Unlike the humidifiers that boil water, these water droplets contain any impurities that are in the reservoir, including minerals from hard water (which then forms a white dust on nearby objects), and pathogens growing in the stagnant tank. Ultrasonic Humidifiers must be cleaned regularly to avoid bacterial contamination which may be expelled into the air.
Disadvantages and risks of Humidifiers
If the relative humidity is over 60%, then the use of a humidifier can allow the reproduction of dust mites or the growth of harmful mold. The relative humidity should be kept between 40% and 60%. Mold growth in the humidifier can be associated with a condition known as Hypersensitivity Pneumonitis (Humidifier Lung) which can cause additional respiratory symptoms and lung damage. If the tap water is used for the humidifier and contains a lot of minerals, also known as hard water, then the ultrasonic or impeller humidifiers will produce a “white dust” (calcium is the most common mineral in tap water), which usually spreads over furniture and other objects. The white dust can usually be prevented by using distilled water and a demineralization cartridge in ultrasonic humidifiers, or cleaning the unit with citric acid or vinegar. Though good vaporizers produce steam that has fewer microorganisms than the water from other types of humidifiers vaporizers do require more energy to boil water (increased electricity use), can burn young children and potentially the heat source in poorly-designed humidifiers can overheat, causing the product to melt, leak, and start fires.