The best size of air purifier for your room

The effectiveness of an air purifier depends on a filtration surface area, resistance to airflow and a reduced pressure drop as well as on the volume of air being filtered. The volume of air filtered depends on the size of an air purifier. The size of a room should match a purifier‘s capacity to clean the amount of air in the room. Therefore the size of a coverage area should match the capacity of an air cleaning device. The most effective air filters , called HEPA, come in a non-portable form. They are very large in size and hence cannot be installed into residential HVAC systems. Since they are so big in size, they have a great capacity in cleaning the indoor air and hence can be used in large commercial areas. However, this type of air filters is also available in a portable form and then their size should be considered before choosing them.

Air purifier size

Most air purifiers are available in various shapes and forms. Therefore a customer should consider what size would be the best to fulfill one’s needs. A bigger room generally has a larger volume of air to be filtered and hence it is obvious that a greater filter is then needed to reach a better quality of indoor air. There are several aspects to be considered in order to choose an air purifier of a proper size to suit in the room. First, a customer should check the square footage of a room. Every air purifier has the square feet listed under “product details: room size”. A customer should know the square footage of a room, where an air purifier is intended to be placed. If the square footage listed matches with the size of a room or is a little bit larger, then such an air purifier is suitable for the room size. Second, a customer should compare room air changes per hour. This indicates how often the air in a room is cleaned.

This is important to know, since the indication shows how frequently an air purifier is able to exchange all the air in a room. The number shows how many times per hour all the air in the room is eliminated from the airborne particles and exchanged with clean air. It also gives the number of times per hour the air is exchanged in a certain size of a room. The best effect is reached when the size of a room listed on an air purifier matches with the size of a customer’s room. Specialists recommend at least 2 room air changes per hour. Some manufacturers list air flow performance ratings when the fan is not switched on. This is an important consideration, since there is an increased resistance to the airflow when the filter media is installed and hence room air changes per hour can decrease even up to 60% of the no load air volume. And finally, a customer should compare clean air delivery rates which indicate how efficiently the air is being cleaned by a certain air purifier.

Clean air delivery rates

Rates are given for the most common pollutants and basically show how efficiently they are removed from the air by an air purifier. Clean air delivery rates are calculated for tobacco smoke, pollen and dust for each air purifier. The higher the rates, the more efficient an air purifier is against the airborne particles. The bigger the air purifier, the more efficient it is against certain allergens. These three factors should be considered before choosing a certain air purifier of a proper size for a room. If an air purifier is too small for a certain room, the quality of indoor air decreases immensely. Hence, special tests should be applied in order to find out whether the size of an air cleaning device suits the room completely and cleans the air in the room from various pollutants. Some customers might consider buying a smaller air purifier that is not appropriate for the room as the smaller the air purifier the cheaper it is. However, saving money on buying unsuitable air purifiers is no good as there is no use of having an inefficient air cleaning device.

Where to place an air purifier

An air purifier is a device used to clean the air from airborne particles, such as dust, mold, pollen, bacteria and viruses, as well as to neutralize indoor odors and gases. The effectiveness of air purifiers depends on the cleaning method used in a device and the size of an air filter. The most effective air cleaners have a high filtration surface area, low resistance to airflow and a reduced pressure drop.

However, this type of an air purifier cannot be installed into residential HVAC devices due to its large size but is available to customers in a portable form. Different manufacturers offer a various range of air purifiers, from simple flat mechanical filters to HEPA air purifiers . Most of these devices are available in both portable and non-portable forms. If an air purifier is a non-portable one, it should be installed into a residential HVAC system. They can be also placed in the ceilings, walls or floors of the buildings. These non-portable air cleaners are mostly used for commercial purposes to clean up the indoor air in medical, pharmaceutical, military, food industry and other objects.

Air purifier purpose

Customers who suffer from asthma, allergies and other respiratory system disorders choose air purifiers which are installed into residential HVAC systems and are non-portable. This allows a higher efficiency in cleaning the indoor air from various pollutants and keep the air quality up to the one recommended by official health organizations. People, who are aware of how polluted the indoor air is and who care about their health, also choose air purifiers in order to improve the quality of indoor air in private houses. This is usually accomplished by portable air purifying facilities. When one has a portable air purifier at home there is a major question: „Where should be a portable air purifier placed in a room?” Most manufacturers recommend the best places for air purifiers in a room in the instructions attached to an air purifier. This makes life of a customer a lot easier. Nonetheless, it is important for a person, who is about to buy an air purifier, to find out a proper placement for an air cleaning device.

Where to place an air purifier

A proper placement provides a higher efficiency of an air purifier and hence the quality of the indoor air increases. If a specific pollutant source exists, an air purifier should be placed near to it to assure the best filtration of the most polluted air. A close placement of an air purifier to the existing pollutant source assures best control of its emissions and nearly removes the source. If there is no such source, an air purifier can be placed wherever it is convenient to a customer. There are only a few directions that a customer should follow in order to achieve best results in air cleaning. An air purifier should be placed across the room from an air conditioning or heating device. It should be also placed further from the vent if one exists. Airflow should not be blocked by any obstacles such as walls or furniture. Therefore one should not place furniture or any other objects directly in front of an air purifier.

Additionally, an air purifier should not be placed directly at the wall. The distance between the wall and the air purifier should be at least 8 inches. If one intends to use an air cleaning device in a bedroom, then such an air purifier should be placed more than a meter of distance away from a bedside. This should be done to avoid health problems. In addition, air purifiers also emit a certain noise level ; therefore it is better to place them away from the bedside for a customer’s silent sleep. Finally, air purifiers should not be placed by an open window since doing so may reduce their cleaning efficiency. Customers should know that an air purifier is needed in every room to reach a high quality of indoor air inside the house. It is recommended that people follow the instructions provided by manufacturers since a proper placement of an air purifier may vary with a type and model of an air cleaning device.

The noise level in air purifiers

Air purifiers mainly consist of an air filter and a fan or a motor. An air filter is used to clean the air from various airborne particles, such as mold, bacteria, viruses, dust, cigarette smoke, pollen and many others. It also helps to neutralize odors and gases in the indoor areas, whereas a fan or a motor makes the air flow into a filter, which can then capture dangerous pollutants and clean the air. Even more, a fan or a motor returns a cleaned, healthy air into the environment and hence is an important part of an air purifier.

However, a loaded fan produces noise. The noise level is one of the characteristics that describe a certain air purifier. Generally, the noise level of an air cleaning device depends upon the type and size of an air purifier. In addition, the noise level depends also on the quality of an air purifier and an air filter.

The noise level in air purifier

One might assume that the bigger the air purifier the higher its noise level. However, it is not necessarily true. HEPA air purifiers , which are considered to be the most qualified and the most effective air cleaning devices in the world, do not necessary, emit a lot of noise. HEPA air cleaning systems are very big but, due to their high efficiency in performance and high quality of fans, they do not have high noise levels. The noise level of HEPA air purifiers varies from 45 to 58 decibels (dB) whereas noise levels of smaller but less efficient air cleaning devices may reach even up to 100 dB. More important, HEPA air purifiers are constructed in such a way that their noise levels may be changed and reduced if used at bedroom mode. A powerful and efficient fan, working at bedroom mode, has a noise level of only 31 decibels. Another advantage of not only HEPA air purifiers but of most high quality modern air cleaning devices is an additional sound sensor. It allows to automatically adapting to the noise level without actually disturbing those in the room.

The sound sensor works in such a way that it induces the cleaning process of an air purifier in noisier surroundings, and hence the fan works louder and more effective but does not disturb the well-being of the inhabitants. When working in a quiet environment, a sound sensor adjusts to a lower setting and is barely audible. Not everybody knows that the noise levels of air purifiers that contain air filters depend upon the maintenance of a cleaning device. Usually, manufacturers recommend to change filters or, in case of electronic precipitators, to clean the systems on a regular basis. This allows an air purifier to work on a more efficient basis as well as it lowers the noise level since the airflow is not constrained. Therefore it is important to follow manufacturer’s directions in order to achieve many benefits by a consumer. To compare noise levels of different air purifier types, ionic air purifiers are claimed to produce less noise than any other air purifiers. Ionic air cleaning devices are said to work silently even at a high mode since they do not contain a fan. In general, most air purifier manufacturers provide information on noise levels of their products.

Noise level types

Usually, there are different noise levels that vary with an air purifier’s cleaning capacity. Most air purifiers are able to work at different speeds which allow choosing the efficiency and the noise level. Noise levels vary from 20 to 40 decibels at a low speed, from 41 to 60 decibels at an average speed and from 61 to 80 and more at a high speed. No matter what speed, none of the air purifiers emit more noise than it is allowed by public health standards. Noise level of an air purifier is an important factor for a customer to know, since some of the air cleaning devices may emit low-frequency noise which could cause severe annoyance, physical and mental stress. Such low-frequency noise may become so irritating that the users tend to turn air purifiers off immediately. The best choice would be to buy an air purifier that has low noise level descriptions, different speed options and a noise sensor that allows an air cleaning device to adjust to different noise levels in the environment. The combination of those three allows customers to gain many benefits.

Air purifier filters

Air purifiers are basically classified due to the method used to eliminate various sized particles and/or gases from the air. The types of techniques available for use in air purifiers include mechanical filters, electronic air cleaners, and hybrid filters for the elimination of particles, and gas phase filters to control odors. There are also air purifiers which produce ozone in order to remove various airborne pollutants. The selection of a type of an air filter depends on the intended use of the air purifier. There are wide applications of an air filter. Air filters are applied in order to protect the HVAC equipment and components, to protect the furnishings decor of inhabited spaces, to reduce housekeeping and building maintenance, to decrease heating equipment fire hazards, and protect the general well-being of residents. The low effective filters in central HVAC systems can be used in order to accomplish most of these requirements. However, to improve the health of residents higher efficiency filters are needed.

Types of air purifier filters

Generally, there are mechanical, hybrid and gas phase filters. Mechanical filters differ in their efficiency of performance due to the type of a mechanical filter. The highest effectiveness filters are HEPA ones but flat and pleated filters are also widely used in central filtration systems as well as in portable air cleaning devices. Hybrid filters contain both a mechanical filter and an electrostatic precipitator or an ion generator in an air purifier, which makes the air cleaning process more effective in terms of eliminating various particles from the environment. Gas phase filters are best for neutralizing different odors and gases in the air. There are several physical mechanisms due to which mechanical filters remove airborne pollutants from the air. Larger particles stick to the filtration medium, smaller particles are eliminated from the airflow by smaller openings in the filter, whereas submicron-sized particles are removed from the air by electrostatic interaction between surface charges of particles and the filter medium. The last method is used in the high efficiency particulate air filters to capture the tiniest particles. The major types of mechanical filters include flat filters, pleated filters and high efficiency particulate filters.

Flat filters

Flat filters contain advance technology paper, textile, slit or expanded aluminum, synthetic, glass, cellulose fibers, or other substance. This type of filter is considered to be a low efficient one and is usually found in most of residential HVAC systems. Flat filter is frequently one-half-inch to one-inch thick and remove mostly large particles while its effectiveness in collecting smaller particles remains low. Another type of a mechanical filter is a pleated one. Small denier fibers are used to increase the filter media density and make a mechanical filter more effective in collecting pollen, dust, smoke, bacteria and viruses. With the bigger filter media density another problem occurs, which is a decreased airflow through the filter. This causes the decrease in the function of a filter. Pleated filter overcomes the mentioned problem making it more effective in eliminating airborne particles from the size of 0.3-10 micron diameter. A pleated filter generally means an extended-surface media filter and its total filtration area is larger than that of a flat filter.

HEPA filters

Another extended surface media mechanical filter is a high efficiency particulate air filter, HEPA. It was earlier called high efficiency particulate arrestor and was first developed in the United States during World War II to protect against radioactive pollution. 10 years after the first HEPA air purifier had been constructed, it was introduced into sales and became an officially registered trademark for very effective filters. HEPA air filters are said to be the most efficient air cleaning devices.  This defines a true HEPA filter in contrast with a near HEPA filter. A near HEPA or “HEPA type” air purifier is the one that did not meet the HEPA requirements and is efficient at 0.3 microns of less than 99.97% but greater than 90%. Though not as efficient as true HEPA filters, “HEPA type” filters are efficient enough to remove dust, pollen, mold, bacteria, viruses and other allergens from the air. And they are cheaper than original HEPA filters.

True HEPA filters have a very high efficiency in eliminating airborne particles but require very high energy costs. Due to their size HEPA filters are not applied in the central HVAC systems but can be used in portable air purifying devices. According to their high effectiveness, HEPA filters are used for medical, pharmaceutical, military, commercial as well as for residential purposes. However, they are not very cheap and require replacement of filters, which are not very cheap, price ranges between $50 and $100 depending on the size of air purifier . No matter the price, HEPA filters have become indispensable for people who suffer from asthma, allergies and other respiratory diseases.

Hybrid filters

Hybrid filters are a later modification of air cleaning devices. They contain a mechanical filter and an electronic precipitator or an ion generator in a central HVAC system or a portable air purifier. A flat or pleated mechanical filter media is charged in the manufactory and has a charge that attracts airborne pollutants to the filter. Particles are then trapped in the filter and are eliminated from the airflow. This makes a media filter more effective in collecting airborne particles but there is an increased resistance to airflow when the filter is soiled. Thus hybrid filters require a periodical replacement. Hybrid filters comparing to HEPA air filters have lower energy cost but are quite effective when new. However, their effectiveness in air cleaning decreases with use and there is an addition cost due to a frequent replacement of filters.

Ionizing charged-media hybrid filter

Another category of a hybrid filter is an ionizing charged-media type filter. This type of an air purifier emits a number of negatively charged ions which then attach to the airborne particles, such as dust, pollen, mold, bacteria and other. These larger particles are then collected by a charged-media filter and eliminated from the air. Ionizing charged-media type filters are claimed to increase the performance of filters and reduce particulate counts in the occupied space. However, their initial cost is relatively high comparing to high efficiency particulate filters (HEPA). There is also no certain data that this type of hybrid filters have a higher efficiency. Electrostatically enhanced filters also exist, although they are not yet available commercially. Experiments have shown that this type of hybrid filters have an increased filtration efficiency. However, they should be first tested under normal environmental conditions not only under experimental ones until they can be introduced into sales for commercial or private purposes.

Chemical and gas filters

None of the above mentioned air filters can efficiently remove environmental gases and odors. Chemical filters are incorporated in many air purifiers in order to remove odors and gases from the air. Gas phase filters are the most effective ones used to neutralize gases and associated odors from the air. Physical adsorption and absorption (or chemisorption) are two major types used to remove solvent vapors, gases and vapors in indoor air, odors and cigarette smoke. Charcoal is widely used for adsorption, as it has a large surface area, low cost and is a stable material. Chemisorption is a chemical process during which the sorbent attracts gas molecules on the surface of the sorbent. An example of such a sorbent is potassium permanganate, an active oxidating reagent that is able to convert formaldehyde gas into water and carbon dioxide which are benign substances. Nowadays more effective methods in gas capture are used. This is possible due to application of two different mixtures rather than one in a gas phase filter. Gas phase filters of this kind are more effective to remove odors and gases than charcoal alone. They are also relatively inexpensive and require no filter replacement. These are easily incorporated in residential HVAC systems as well as in portable air cleaning devices. In general, all air purifiers remove airborne particles from the air but their effectiveness in the process depends on the type of filter used. The most efficient air purifier is the one with a HEPA filter. And the most effective device in removing gases and vapors is a gas phase filter. These two used in residential HVAC systems or portable air purifiers meet most of the clean environment requirements.

Air purifier price

Air purifiers differ each from another in types and brands. Air cleaner types depend on the manner and method that is used in order to clean the air from various airborne pollutants. Various companies produce different brands of air cleaning devices. The cost and price of each air cleaner depends very much on the type, efficacy, size, coverage area and brand of the device. In addition, retail prices of the same air purifier may vary from dealer to dealer.

Ozone air purifier price

Ozone air purifiers , with ozone used in them, are best to be chosen to clean the areas from microorganisms and fungi. Ozone also has deodorizing properties and therefore ozone generators can eliminate unpleasant odors of indoor areas.

Biozone air purifiers cost:

Size Price
500 sq. ft. device $150 – $200
1000 sq. ft. device $230 – $250
2000 sq. ft. device $280 – $300
3000 sq. ft. device $300 – $350

UV air purifier price

UV air purifiers use UV light to eliminate various pollutants from the indoor air. Various brand names are known which use ultraviolet light alone or, most frequently, in combination with other filters, such as HEPA or carbon filters.

Combined air cleaners of UV light, HEPA and carbon filters cost from $450 to $600 depending on the brand and area coverage.

True Air UV filter price range: $114$200

Ionic air purifier cost

Ionic air purifiers generate negatively charged ions which then attach to airborne particles and eliminate the following from the air. The best known brand name for this type of air purifying devices is Friedrich . Price range for Friedrich air purifier: $400$550

The price of Friedrich Air purifiers depend upon the model of the device. Most Friedrich ionisers have a coverage area of 465 sq. ft.

HEPA air purifier cost

HEPA air purifiers are known for their high air cleaning properties. They are considered to be the most efficient type of air cleaning method these days. HEPA filters eliminate almost all the airborne particles, such as dust, mold, pollen, volatile gases, various microorganisms and cigarette smoke. There are various companies that produce HEPA air purifiers :

Air purifier brand  Price
Air-O-Swiss HEPA air purifier $350 – $450
Austin Air HEPA air purifier $450 – $550
IQAir HEPA air purifier $600 – $1500
TrueAir HEPA air purifier with UV germicidal lamp $180 – $300

Those, who wish to buy a HEPA air purifier, should remember that maintenance and change of filters would cost approximately $80$100 per year.