Air Purifiers FAQ
Air purifiers are appliances that remove particles (dust, hair, pollen, bacteria, viruses, etc.) and harmful contaminants from the air that affect lungs, irritate airways, and worsen allergies. Air purifiers pass these particles through highly efficient air filters to improve air quality. These devices are often shaped like sophisticated portable fans and come in both domestic and industrial models.
What’s the solution? Air purifiers! They’re designed to clean the air that circulates in your home so that your indoor air stays clean, and your family can live a healthy life.
According to the EPA, indoor air contains more than five times more contaminants than outdoor air. Air inside a home often circulates unfiltered for days before being replaced. Unfortunately, air that is usually filled with contaminants like dust, pollen, or pet dander, which can cause severe respiratory problems and chronic fatigue. Below diagram shows different pollutants and their particle size in microns (one-one millionth of a meter).
Air purifiers are the best way to clean your air indoors. They also help maintain a healthy environment by removing pet dander, mold spores, ragweed and more. If you don’t think an air purifier is the right choice for your home; here are 10 reasons to reconsider: 1. Air purifiers ensure your family is breathing clean air.
2. Air purifiers remove unpleasant odors.
3. Air purifiers trap airborne allergens released by pets.
4. Air purifiers help neutralize smoke.
5. Air purifiers trap dust.
6. Air purifiers remove up to 99 percent of airborne bacteria.
7. Air purifiers combat seasonal allergens.
8. Air purifiers stop sickness and germs and viruses from spreading.
9. Air purifiers keep your lungs healthy.
10. Air purifiers fit everywhere.
Air Purification Systems are generally separated into 3 categories:
1. Mechanical air purifiers, which clean the air by trapping dirt in a filter made of some type of media.
2. Electrostatic air purifiers trap dirt by electronic magnetism.
3. The Third uses some other device to clean the air of specific items; for
instance, UV filters remove live organisms.
|Technology||Efficiency Range||Particle Size||Advantages||Disadvantages|
|Fiberglass Media||3 – 5%||0.3 – 1 micron||Inexpensive||Very low efficiency|
|Electrostatic Media (No electric charge)||15 – 30%||0.3 – 1 micron||Relatively inexpensive||Efficient only on larger particles|
|Electret Media (Electrically charged)||40 – 90%||0.3 – 1 micron||High efficiency on large-medium size particles||Low efficiency on smaller particles|
|Medium Efficiency Media||35 – 60%||0.3 – 1 micron||Low airflow resistance||Require replacement filters|
|High Efficiency Media||60 – 95%||0.3 – 1 micron||High efficiency on many smaller particles||High airflow resistance|
|HEPA Media||0.997||0.3 – 1 micron||High efficiency on many smaller particles||High airflow resistance|
|Ozone Generator (emission of the highly reactive molecule-O3)||inconclusive testing information||0.3 – 1 micron||Ideal for removing odor after fires||No particle collection May irritate asthma Considered dangerous by the EPA and OSHA|
|Ionizer (negatively charged ions)||inconclusive testing information||0.3 – 1 micron||Relatively low cost||No particle collection Largest particles may be re-circulated|
|Electrostatic Precipitator||Up to 97%||0.01 microns||High efficiency on many smaller particles||Filter must be maintained|
When air passes through an air purifier, contaminants, debris, and microscopic particles are removed to provide a high level of air quality. Some purifiers are designed to remove specific types of contaminants. You may want to use a filter made of paper, mesh, fiber, carbon, or other materials depending on your budget and the type of air quality issue that you are looking to address. Thus, to effectively do their job, air purifiers need to perform 2 actions:
1. Create airflow through the air purifier (measured in CFM). These devices need to gather all the unclean indoor air to have the ability to remove numerous pollutants.
2. Use effective filters to purify the air. The filters are the heart of every air purifier; they capture the pollutants in the indoor air. The created clean air is expelled out of the air purifier by the continuous airflow.
The basic air purifier works by creating an airflow through its filtration system (with several filters that gather air pollutants).
The key component of any air purifiers is the air filter. Air is generally filtered through meshes that remove harmful particles that can cause allergies or other health issues. There are 4 primary types of filters used in modern air purifiers:
1. Nylon Filters: These are the same filters that air conditioners use. Nylon filters are simply thin meshes that retain dust and other large particles. Nylon filters are also known as pre-filters. Since these filters are made out of foam or nylon, they can be washed and re-used. Thus not only the pre-filters act as good blockers for large particles, they have a good longevity too.
2. Active Carbon Filters: This filter is composed of pure, porous carbon that transforms offensive air particles into solids through a chemical process. Activated carbon is made up of several compounds that only allow the passage of particles smaller than 50 nm (Nanometers). This part of the filter traps tiny biological particles that cause health issues and odors.
3. Synthetic Bag Filters: Better known as the G4 filter, this variant looks like a plastic sheet but contains ultra-thin nylon yarns. It functions similar to the nylon filter, but the meshes are treated with chemicals to filter even finer particles of dust or bacteria.
4. HEPA Filters: High efficiency particulate air (HEPA) filters are quiet, compact, and extremely effective. According to the American Society of Mechanical Engineers, HEPA filters must be able to remove 99.97% of small particles (0.3 micrometers) from any air that passes through them.
5. HEGA Filters: HEGA stands for High Efficiency Gas Absorption, and this type of filter was developed about a decade ago by the British Army as a defense against chemical warfare. HEGA filters are composed of a carbon cloth and are considered to be many times more efficient than granulated activated carbon at adsorption of gaseous pollutants, chemicals, and odors.
HEPA is a type of pleated mechanical air filter. It is an acronym for "High Efficiency Particulate Air [filter]" (as officially defined by the U.S. Dept. of Energy). This type of air filter can theoretically remove at least 99.97% of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns (µm). The diameter specification of 0.3 microns responds to the worst case; the Most Penetrating Particle Size (MPPS). Particles that are larger or smaller are trapped with even higher efficiency. Using the worst-case particle size results in the worst-case efficiency rating (i.e. 99.97% or better for all particle sizes).
All air cleaners require periodic cleaning and filter replacement to function properly.
The Minimum Efficiency Reporting Values, or MERVs, report a filter's ability to capture larger particles between 0.3 and 10 microns (µm). • This value is helpful in comparing the performance of different filters
• The rating is derived from a test method developed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) [see www.ashrae.org ].
• The higher the MERV rating the better the filter is at trapping specific types of particles.
|MERV Rating||Average Particle Size Efficiency in Microns|
|1-4||3.0 - 10.0 less than 20%|
|6||3.0 - 10.0 49.9%|
|8||3.0 - 10.0 84.9%|
|10||1.0 - 3.0 50% - 64.9%, 3.0 - 10.0 85% or greater|
|12||1.0 - 3.0 80% - 89.9%, 3.0 - 10.0 90% or greater|
|14||0.3 - 1.0 75% - 84%, 1.0 - 3.0 90% or greater|
|16||0.3 - 1.0 75% or greater|
Ion generators act by charging the particles in a room so that they are attracted to walls, floors, tabletops, draperies, occupants, etc. Abrasion can result in these particles being resuspended into the air. In some cases, these devices contain a collector to attract the charged particles back to the unit. While ion generators may remove small particles (e.g., those in tobacco smoke) from the indoor air, they do not remove gases or odors, and may be relatively ineffective in removing large particles such as pollen and house dust allergens.
Ozone, a lung irritant, is produced indirectly by ion generators and some other electronic air cleaners and directly by ozone generators. While indirect ozone production is of concern, there is even greater concern with the direct, and purposeful introduction of a lung irritant into indoor air. The Food and Drug Administration has set a limit of 0.05 parts per million of ozone for medical devices. So, when considering to buy an ionizer or an ozone generating air purifier, make sure the level of ozone it generates is within the safety zone.
UVC light air purifiers kill biological organisms such as bacteria and viruses. UVC is a kind UV light with the wavelength of about 254 nanometers. When a living cell passes close enough to a UVC light the DNA of the cell is damaged. These cells have to be exposed to UVC light for extended periods. The length of time needs varies from cell to cell and the intensity of the UVC light that hits the cell. The closer the cell comes to the light bulb the better. UVC light is especially effective on viruses and bacteria. The average bacterium is killed in 10 seconds if it is within 6 inches of the UVC Bulb. For an air purifier this means the bacteria would probably have to go through the filter several times. Some bacteria are collected by the filters and exposed to the UVC light for an extended period of time.
• Room Size: Make sure the purifier can change the air several times an hour. Most manufacturers will provide consumers the appropriate room size that the air purifier can clean efficiently and effectively.
• Efficiency: This refers to the ability of an air purifier to effectively clean the air and is presented as a percentage of particle removal in terms of particle size, i.e. HEPA has an efficiency of 99.97% for particles of 0.3 microns and larger.
• Technology: What technologies are used to filter the air? For instance HEPA, HEGA, UV, Ion, Carbon, etc.
• Noise Level: You want this to be as low as possible, but realize some of the better air purifiers do make noise. Quieter doesn't necessarily mean better.
• Warranty: Learn about the warranty available for the unit you are considering.
• Indicator Lights for Filter Changes: Some units have them. It's not necessary, but is very convenient.
• Separate Filters: Does the unit have a pre-filter to increase HEPA filter efficiency?
• Eliminating Viruses: Does the unit have a mechanism (i.e. UVC, Carbon Cloth, etc.) that eliminates viruses?
• Size and Look of the Air Purifier: Some air purifiers are big and ugly. Others are sleek and pleasing to the eye.
To choose the right size air purifier for your needs, consider the square footage of the room you want to purify. If you have allergies or asthma and are looking for an air purifier to help manage your symptoms, you should also consider an air purifier’s air change per hour (ACH) rate. ACH refers to the number of times an air purifier can filter the entire volume of air in the treatment space each hour. Effective air cleaners should have enough capacity to clean a room at least 2 – 4 times each hour. A 20’ by 20’ work or living space can efficiently and effectively be cleaned by a model with a 210–275 cfm rating. A rate of four air changes per hour also that the air purifier thoroughly cleans the air. Below is a rough size guide for air purifiers with an ACH of four:
• Small: These air purifiers are designed for personal space or rooms up to 299 square feet.
• Medium: Find an air purifier for rooms between 300 and 699 square feet.
• Large: Use these air purifiers in rooms between 700 and 1,900 square feet.
There are several things to consider when buying an air purifier to ensure that you get the best performance:
• Where will you use the purifier?
• Do you have specific needs such as removing pet dander or smoking residue?
• Compare the CADR ratings.
• Purchase a device with HEPA filter technology.
• Never buy a purifier with plastic filter housing.
• Get a purifier with the lowest noise rating possible.
• Consider the cost of replacement filters and maintenance.
ACH: Air Change per Hour rate
Air Movement Rate: Air movement rate, measured in cubic feet per minute (cfm).
CADR: Clean Air Delivery Rate
HEPA: High Efficiency Particulate Air [filter]
HEGA: High Efficiency Gas Absorption [filter]
MPPS: Most Penetrating Particle Size.