Ozone generators

The second type of air purifiers employs a chemical modification process instead of mechanical or electronic filters to purify the air. They release a small amount of ozone, which is relatively harmless to humans but is lethal to airborne bacteria and viruses.

Ozone generators

Ozone, sometimes referred to as activated oxygen, is a very strong oxidizer and has been used in water cleaning since 19th century. Beneficial results can be achieved by introducing a large amount of ozone into areas where people are not exposed. Great concentrations of ozone are used to eliminate microbial growth in meat storage, and to prevent from microbial growth from fire or flood damaged houses. However, ozone has been introduced in ozone generators for cleaning the air where humans are exposed. There is a huge concern of positive and negative effects of ozone in nearby areas. Ozone created by ozone generators circulates in the air and reacts chemically with different airborne particles.

Many manufacturers claim that harmless end-products, such as oxygen, carbon dioxide and water molecules, are formed during the chemical reaction. Unfortunately, there are no guarantees that certain chemical reactions could not produce toxic substances. One should not forget that ozone itself can be harmful and toxic if improperly used. The U.S. federal government has set safety requirements for exposure to ozone. On the other hand, manufacturers produce ozone generators that emit ozone at safe levels. The Food and Drug Administration (FDA) requires ozone release of indoor medical devices to be no more than 0.05 ppm. Therefore ozone sensors attached to every ozone generator should be used in order to control the concentration of ozone in a certain area. However, due to excessive cost most manufacturers provide with ozone generators that do not have ozone sensors attached. This generally means that such an ozone generator cannot control the output of ozone at safe limits.

Ozone generators effiency

Hence manufacturers recommend a certain model of an air purifier to be used in a certain size of a room so that the concentration of ozone would not break safety limits. If the consumer uses such a model in a smaller area than recommended by a manufacturer, there is a big danger to people that are in the room. Although most of companies claim that the efficiency of ozone generators is high, experiments show that not all the airborne allergens can be cleared from the air effectively. Chemical reaction process with ozone, to eliminate certain pollutants, takes months or years. Experiments show that not all the chemicals can be removed during chemical reaction process with ozone. Ozone generators are also of small use in clearing the air from dust and mold, the most irritating allergens. However, when constructed together with an air ionizer, an ozone generator could be of greater efficiency to eliminate dust, pollen, mold and tobacco smoke from the air.

Some companies also claim that ozone generators are an ideal option for removing room odor, since ozone reacts with most of the volatile gases to neutralize their odor. Finally, there are many side effects of ozone gas. Higher concentrations of ozone gas in the air that people breathe can be extremely harmful to the respiratory system. Scientists claim that certain side effects are throat irritation and cough, decrease in lung function, chest pain, higher susceptibility to respiratory disease and aggravation of asthma. Hence biozone air purifiers are not a good option for people suffering from respiratory tract disorders. In conclusion, due to the possible side effects of ozone, ozone generators should be used with a high precaution. They should not be used by people suffering from certain respiratory disorders. An ozone sensor should be used with every ozone generator despite excessive costs.

What is an air purifier?

An air purifier is a device used to free air from contaminants, such as dust, smoke, gas, pollen and mold. Most air purifiers also remove harmful bacteria and viruses from the air. Various methods are used to clean air from various indoor allergens. This includes air purifier filters , adsorbents like charcoal, and electrostatic charges. Various air purifiers can be most beneficial for people who suffer from allergies, asthma, chronic obstructive pulmonary disease and other respiratory disorders.

Air purifier types

There are various kinds of air purifiers: ionic air purifiers , HEPA air purifers , HEGA and ultraviolet light air purifiers. These differ from one another according to different techniques used in clearing the air. There are also room, home and commercial air purifiers, and these differ according to air purifier size and area coverage. Many different companies claim to have the most efficient air purifiers. However, there is some controversy specifically involving ionic air purifiers. This is mostly due to a questionable effect of negative ion generators. Ionic air purifier technology is based on releasing charged particles which then attach to smaller indoor allergens in the air to create larger particles. They are then cleared from the air.

Another type of air purifier is the HEPA air purifier . HEPA is an abbreviation for “high efficiency particulate air”. Companies must fulfill high HEPA requirements. A HEPA air purifier can clear from the air at least 99.97% of any particles with a size of 0.3 micrometers or larger. The first HEPA air purifier was constructed in the 1940s to protect against radioactive pollution. It was introduced into sales in the 1950s and became an officially registered trademark for very effective air filters. Nowadays HEPA air purifiers use photo-catalytic oxidation technology to remove airborne particles from the environment. They are widely used in the home as air purifiers to get rid of allergens in the air. They are also more than ideal to remove room odor. One should know that “HEPA type” air purifiers are those that did not meet the HEPA requirements. There is another type of air purifier, the HEGA filter. HEGA stands for “high efficiency gas absorption”. The HEGA filter was first designed by British military to defend against chemical warfare. A carbon cloth filter is used in HEGA air purifiers, hence it has become popular in residential air purifiers.

Ultraviolet light used in air purifiers eliminates organic compounds, such as harmful bacteria and viruses, in the air. They also are perfect to remove odors. They are all portable, but are larger than ionic air purifiers. Home purifiers are designed especially for home use. They can be used in a single room area or cover the whole household. They eliminate dust and remove pollen and mold spores. They are also useful for eliminating gaseous contaminants, purifying smoke, and reducing odors. They are small, portable and very easy to use.

Room air purifiers are similar to home purifiers but they are smaller and used for smaller coverage areas. Room air purifiers are a good option for bathrooms, bedrooms, kitchens, and living rooms. The technique used in room air purifiers is similar to that used in home air purifiers. Commercial air purifiers are constructed for large commercial areas and greater pollution zones. They are an ideal option for shopping malls, hospitals, bars, and clubs to clear the area of gaseous contaminants, cigarette smoke, and dust. They are also used for organic contamination. Air purifiers are designed for private and commercial purposes. They are indispensable for people who suffer from allergies and other respiratory diseases. They are also indispensable for bars, cafes and night clubs, where air purifiers are used in order to eliminate cigarette smoke. In conclusion, there are various types of air purifiers, each used to accomplish different purposes.

Biozone air purifier features

This basically means that such an ozone generator cannot control the output of ozone at safe limits. Therefore some agencies claim to have introduced a new method in ozone concentration control.

Biozone air purifier features

The method does not allow the concentrations of ozone in the indoor air to exceed recommended, safe levels. It is based on the principle that the biozone air purifier reduces the amount of ozone being produced automatically, thereby keeping the concentration at low levels with no hazard to human health. Manufacturers who produce biozone air purifiers without ozone sensors have recommendations at which such devices should be only used in a certain size of a room. There could be hazardous effects on health if the consumer decides to use such a biozone air purifier in a smaller room, since ozone accumulation would exceed safe levels without a doubt.

There have been also some modifications introduced by some agencies in the process of an ozone generation. A primary corona discharge (high voltage electricity) method is used in most biozone air purifiers, while other manufacturers start implementing ultraviolet lamps in the production of photolic ozone. Additionally, ultraviolet lamps also provide ultraviolet germicidal irradiation (UVGI). This process is used in special ultraviolet light air purifiers enabling them to remove harmful bacteria, mold and viruses; thereby providing an efficient infection spread control in the indoor air.

Advantages and disadvantages

It is important to know that like all the machines, biozone air purifiers have both advantages and disadvantages. Despite all the disadvantages ozone air purification systems have been used for many decades in air cleaning devices. They have been established to be efficient in their function, cost effective, low energy use and low maintenance requirements. Biozone air purifiers are suitable for commercial and private purposes, where air purification is needed. These devices are more than ideal for the elimination of room odor. Since biozone air purifiers could cause many side effects, it is important to use these machines with high precaution. An ozone sensor is a must in all the models, despite excessive price. Then a biozone air purifier can be a helpful tool in cleaning the indoor air from various airborne contaminants.

Ionic air purifier

Ionic air purifier is a device that is able to eliminate various types of airborne particles and pollutants from the air through dispersing negatively (and/or positively) charged ions or ozone. According to what type of substance is dispersed through an ionic air purifier, there are two types of air ionizers: negative ion generators and ozone generators. The first type of air purifiers disperse negatively charged ions into the air. These negatively charged ions occur naturally by waterfalls or after thunderstorms and have an ability of cleaning the air from various pollutants. Generated by ionic air purifiers , negatively charged ions can then be attracted by positively charged airborne particles, such as dust and mold. These airborne particles can then attach to the nearby surfaces, such as walls or furniture, leaving the air cleaner.

Ionic air purifier

The simplest types of air ionizers use static charges to eliminate pollutants from the indoor air. The airborne particles attached to negatively charged ions then deposit on the walls, floors, curtains and other surfaces in the area. The disadvantage of such air cleaners is that they cannot remove the deposits of pollutants from any surfaces. More complicated units are constructed in order to prevent the deposition of pollutants to surfaces. They also release negatively charged ions causing airborne particles become charged. These particles are then collected in a cleaner on an electrostatic charged panel filter. In other ionizers, negatively charged particles are passively moved back to the ionizer, which has a positively charged sleeve or cover. There are two types, a one-stage or a two-stage, design for airborne particle collection. A two-stage design is more complicated, more efficient and, hence, more expensive, while a single-stage design is less effective since a charged medium is used both to charge and collect airborne pollutants.

Ionic air purifier features

The effectiveness depends on the size of the collecting plates, the flow rate and the strength of the electrical field. The particle collection efficiency is reduced due to a longer use, as the collecting plates become covered with the particles. There are a lot of advantages concerning ionic air purifiers . An ionized room offers many health benefits, therefore air ionizers are being chosen by people who suffer from allergies, asthma and other respiratory diseases, since ionic air purifiers are efficient in eliminating dust, pollen, mold, cigarette smoke, harmful bacteria and viruses from the air. In addition, in combination with ozone generators ionic air purifiers become even more effective as they can remove unpleasant odor. These devices are very cost effective due to their low energy costs because of low pressure drop. The precipitating cell is reusable and it only requires periodical cleaning that saves long-term filter replacement costs. However, as all devices, ionic air purifiers also have a few disadvantages. Although the airflow through the units remains the same with use, ionic air purifiers become less efficient with time. Collecting cells require frequent cleaning and can release ozone as a by-product. And when price is concerned, ionic air purifiers have a relatively high initial cost including expensive installation. Additionally, charged particles can discolor room walls, furnishings and other room surfaces.

Advantages of ionic air purifier

Despite all the disadvantages of ionic air purifiers and ozone generators, these devices are widely used for residential air purification. There are different modes of ionic air purifiers, such as room, home air purifiers. They are cost effective, portable, very easy to use, efficient in cleaning the air from various pollutants and odors, and requires easy maintenance. Although they are less effective than HEPA air filters but also are less expensive. Some manufacturers claim that the efficiency of ionic air purifiers equals to that of HEPA air filters, however, this is misleading. There are also some claims that there is a possibility to produce negative ions without actually producing ozone as a by-product but there are no evidence based data to prove such information. One should know that even though ionic air purifiers work well, they are of a limited use when very small particles are concerned, since they cannot remove very small particulates from the air. Recent experiments unfortunately show that ionic air purifiers even combined with ozone generators are less effective in removing dust, pollen, mold and tobacco smoke than any other air purifiers. Since there are so many controversy discussions and debates concerning ionic air purifiers, it is every consumer’s choice whether to use them or not.

HEPA air purifier

HEPA air purifiers are said to be the most efficient air purifiers. HEPA stands for “high efficiency particulate air” which means that a HEPA air purifier can theoretically eliminate from the air at least 99.97% of any particles with a size of 0.3 micrometers or larger. 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%.

HEPA air purifier

The history of HEPA air purifiers began in 1940’s in the United States where a very first HEPA air purifier was developed. Its purpose was to protect against radioactive pollution. It was then modified for people’s private use and introduced into sales within 10 years after the first HEPA air purifier had been constructed. Since the efficiency of HEPA air purifiers was very high, they became very popular among customers worldwide. Even more, a HEPA filter became an officially registered trademark for very effective filters. U.S. Department of Energy has very high stated requirements that companies must pass in order to fulfill the HEPA filter requirements.

HEPA air purifier features

HEPA filters are still used in order to protect the public and the environment against radioactive pollution in nuclear power stations and other high technology industries, such as aerospace, military cleaning rooms and similar objects. As they are highly efficient in clearing the air from harmful viruses and bacteria, HEPA air purifiers are widely used in hospitals, pharmaceutical companies and other health care centers. Due to their ability to eliminate other various indoor allergens, such as dust, mold spores, smoke and pollen from the air, HEPA filters are widely used in the houses to clear the air from the above mentioned particles. Unlike some other air purifiers, HEPA air purifiers are very efficient in getting rid of the unpleasant room odor. Hence they are a first choice for cafes, bars and restaurants in order to eliminate cigarette smoke there. According to the size of a HEPA air purifier and area coverage there are various types of such air purifiers. There are room, home and commercial HEPA air purifiers. Home air purifier is used for private purposes at home. Such air purifiers with a HEPA filter inside can cover a single room or the whole house area. People, who suffer from allergies, asthma or other respiratory disorders, choose HEPA air purifiers.

Room HEPA air purifiers

Room HEPA air purifiers are similar to the home air purifiers but are smaller and covers a smaller area to be cleared. They are more then ideal in bathrooms, kitchens, bedrooms and other parts of the house where air purification is needed. Room air purifiers are more easily used than home air purifiers as they are small, portable and often do not need to be changed.

Commercial HEPA air purifiers

Commercial HEPA air purifiers are the largest air purifiers of the kind. They are used in large commercial areas and greater pollution zones. Such air purifiers are likely to be not portable and are used in hospitals, large technology industries, shopping malls and other similar objects. As mentioned above, commercial HEPA air purifiers are useful not only in protecting public health and environment against radioactive particles but also in clearing the air from cigarette smoke, pollen, dust, mold, unpleasant odor and organic contamination, such as bacteria and viruses. However, HEPA air purifiers are mostly used for commercial purposes. They are constructed for disk drive, clean room, medical device, nuclear, semiconductor, food, pharmaceutical and other industries requiring contamination control.

HEPA filters

There are special type filters constructed for hospital applications. These are vector filters, as well as ceiling filters for surgical and patient environments. HEPA filters are indispensable for hospitals where mobile HEPA air purifiers are used for the highest contamination control. They allow clearing the air from any airborne pathogens that may cause airborne infection, such as tuberculosis. HEPA filters can also protect particularly against drug resistant strains. HEPA filtration system reduces the risk of airborne infection for patients, medical staff and other healthcare workers. HEPA air purifiers can be located in isolation rooms, admittance, waiting, emergency rooms and other critical areas of use. They are most effective when placed closest to the source of contamination. This stops the migration of harmful airborne pathogens, and hence stops the spread of airborne infection among patients and healthcare staff. Various techniques are used in HEPA air filters to aim the highest efficiency in clearing the air from different indoor allergens that may be harmful to the public and the environment.

HEPA air purifier cost

There are many different manufacturers that offer different HEPA air purifiers. A small modification may cause a big rise in price, so a customer should be aware that a big price does not necessarily guaranty a greater efficiency in performance. Customers should know that the efficiency of a filter reduces if it is not changed regularly. Therefore, all air purifiers must be tested periodically for a better pollution control. Customers should not forget that “HEPA type” air purifiers have much lower air cleaning effectiveness than true HEPA air filters, hence are cheaper. However, HEPA air purifiers are the most effective ones and their price is affordable. HEPA air purifiers have changed a lot since the original air purifier of such type was first invented. There are various HEPA filters aimed for different purposes. There are a lot of advantages of a HEPA filter. The major ones are high efficiency in performance, which increases with use. A HEPA filter has a long free of maintenance life cycle which can be up to 5 years if used with pre-filter. However, there are a few disadvantages, such as high cost, due to periodic replacement of filters, the price of each ranging from $50 to $100 depending on size. HEPA filters can be rarely used for residential purposes concerning their size and huge power requirements. There is an increased energy cost because of a need for a powerful fan. Despite their huge energy needs and costs the popularity of HEPA air purifiers is steadily rising both in private and industrial areas, since they are the most efficient air cleaning devices of a kind.

UV air purifier

Ultraviolet (UV) light has long been known for its purifying power. Used at certain dosage it helps to destroy all the airborne pathogens, such as bacteria, viruses, mold etc. UV purifiers were first used in cleaning other substances, such as water, from various pathogens. A first UV air purifier was constructed a few decades ago and was first used in medical and dental facilities. These devices were then modified and commercialized and are now available for residential and commercial purposes. Nowadays there are many different companies that produce UV air purifiers alone or in combination with other air cleaning devices, most frequently with HEPA air filters.

The purpose of UV air purifier

Various UV air purifiers are used to eliminate airborne infection in medical or dental objects, or in any other places where a big risk of infection exists. The method used in air purifiers of this kind is called Ultraviolet Germicidal Irradiation (UVGI). Due to the small size of various viruses and some bacteria, they cannot be caught and eliminated from the air by simple media filters. Hence a UV air purifier is needed to clean the air from airborne pathogens and prevent from the spread of infection. Airborne microorganisms are being eliminated from the air when exposed to specific levels of UV radiation. These levels vary with the type and concentration of bacteria or viruses present in the air.

Moreover, UV light can be a strong weapon for destroying other pollutants and allergens in the air, such as dust, pollen and toxic volatile substances. This is maintained due to photochemical process, which takes place when particles are exposed to UV light energy. When this process reaches certain level, UV light is useful and effective in destroying the above-mentioned particles as well as biological contaminants, such as bacteria, viruses and fungi. UV air purifier usually consists of two main parts: a UV lamp and a media filter. A filter may be flat, pleated of high efficiency particulate air (HEPA) filter. Aflata air purifier filter generally consists of a low packing substance and is not efficient enough when used without UV lamp. A pleated filter has an increased filter density and hence higher efficiency in clearing smaller particles from the air. And finally, a HEPA filter is considered to be the most efficient air-cleaning device that has the ability of eliminating at least 99.97% of all airborne particles of 0.3 micron diameter and larger. HEPA filter is therefore most frequently used in UV air purifiers. Another part of UV air purifier is a UV lamp, which has a germicidal power against biological airborne pollutants. The germicidal efficiency of this lamp, and hence of a whole UV air purifier, depends on the time of exposure of a microorganism to the killing UV light and the intensity of UV lamp. Different airborne pathogens require different levels of UV light and different exposure times.

Ultraviolet lamps

UV lamps are most effective in still air at an average temperature of 23 degrees Celsius. In general, one should know that the greater the size of the UV lamp, the bigger the output of ultraviolet germicidal irradiation. However, not all the companies have UV air purifiers that emit a high UV dosage that is required in order to kill various germs and viruses. Such UV air purifiers have a UV lamp only to maintain filters clean from fungi and bacteria growth. These devices cannot destroy airborne microorganisms since their UV dosages are too low. UV air purifiers are available for private and medical facilities. In residential areas and homes these devices are used in a portable mode whilst in medical facilities and hospitals they may be installed into walls and ceilings. UV air purifiers are a must in hospitals, medical or dental facilities and should be located in emergency rooms, surgery theaters, general wards of infectious patients and other areas of high risk of airborne infection. When residential or home UV air purifiers are considered, it is every person’s decision whether to use it or not. UV air purifiers are very helpful to people who suffer from different allergies, since these devices clear the air from various allergens, including dust and pollen. People who suffer from frequent respiratory tract diseases and infections of different body organ systems may also choose a UV air purifier due to its high efficiency in destroying airborne microorganisms.

UV air purifier and HEPA filters

There are a lot of various investigations made in order to find out more about the benefits of the use of UV lamps and HEPA filters in the same unit. All of them claim that UV air purifiers are more efficient than HEPA filters alone, since some viruses can penetrate HEPA filter. A UV air purifier makes the viruses impossible of such action. Some research results show that the use of UV air purifiers in the ventilation system helps to eliminate up to 99% of all airborne germs. Even more, it has been shown that people residing in the area maintained with a UV air purifier have less respiratory symptoms and complaints as well as less work-related breathing problems. Therefore, U.S. Centers of Disease Control recommend to apply UV air purifiers and HEPA filters not only in medical facilities but also in government buildings, residential areas, restaurants, schools and kindergartens in order to increase indoor air quality and prevent from infectious diseases. Moreover, there are some recommendations to use UV air purifiers in homeless shelters in order to stop the spread of dangerous airborne infectious diseases, such as tuberculosis (TB). When the price of UV air purifiers is considered, they are not much more expensive than HEPA filters alone. The price differs with the manufacturer but is at a decent level, especially considering all the advantages of a UV air purifier . UV lamps may be used for up to 5 years and then should be changed if they are not working properly. However, the lifetime of UV lamps may vary with different manufacturers and types of lamps.

Advantages and disadvantages of UV air purifier

It is very important to mention, that UV light may be destroying to people’s skin and eyes when exposed directly at high levels. However, there is no doubt that UV air purifiers are safe when used in inhabited areas and are of no damage to people. This is provided by the mechanism that UV light acts isolated only in the air-cleaning device. Hence, only the air that passes through a UV air purifier is affected by UV light power and is being sterilized. UV light does not escape the device and therefore cannot affect people in the coverage area. Scientists claim that intense sunlight kills or destroys most of the airborne microorganisms in the outdoor air. The indoor air is from 6 to 10 times more contaminated with dangerous germs compared with the outdoor air. Therefore UV air purifier is a possible effective option to improve the quality of indoor air, destroy all the airborne pathogens, purify the air from various allergens and maintain an efficient disease and infection control. Due to these abilities and advantages, UV air purifiers are becoming more and more popular among people worldwide.

Biozone air purifier

Ozone is a main component of the earth’s upper atmosphere, where it is produced during a complex photochemical reaction. It is sometimes referred to as activated oxygen and is produced in the outdoor air during electrical thunderstorms or close to waterfalls. Many scientists have tried to identify the chemical structure of ozone but none of them succeeded to do so up until the middle of the 19th century when Christian Schonbein, a German researcher, named the compound ozone after a Greek word “ozein”. The chemical structure of the compound was set as a triatomic oxygen. This basically means that ozone molecule contains of three oxygen atoms. Therefore ozone is another molecular form of ozygen, having totally different physical and chemical properties.

 

Biozone air purifier

Ozone is relatively stable in the air and can be a strong oxidizer in both water and air. According to these properties, ozone has been used since the end of the 19th century in drinking water cleaning methods. As an oxidizer, nowadays ozone is used in many water treatment applications, such as the treatment of municipal water and wastewater, marine waters, swimming pools, beverage businesses, food processing and many others. The purpose of water purification by ozone is not to kill all harmful microorganisms but to keep their numbers down at safe levels to achieve an efficient disease control. Known as an efficient compound in water purification, ozone was introduced into air cleaning systems a few decades ago. It was first used in uninhabited environments, such as fire or flood damaged houses, to prevent from microbial growth there.

Today, ozone is used in cleaning the indoor air in residential areas. This was made possible after the invention of an ozone generator , a device which emits ozone gas at safe concentrations in order to eliminate airborne particles, including dust, pollen, fungi, cat and dog dander, odor and harmful microorganisms from the indoor air. The main principle of ozone action in cleaning the air is a chemical reaction between ozone and airborne pathogens. However, certain by-products are released during the reaction. Even though some manufacturers claim them to be only harmless oxygen, carbon dioxide and water molecules, there is no prove that specific chemical reactions could not form toxic compounds. Biozone air purifiers have been known for over a hundred years due to their advantages in air purification and sanitation processes. Ozone gas acts as a bactericide, viricide, fungicide and deodorizer.

These ozone properties are widely accepted by the scientific community. Ozone, emitted at safe levels, has been known as an efficient odor neutralizer, since it reacts with most of dangerous volatile compounds. Since ozone is a strong oxidizer, it is used to kill airborne microorganisms, including harmful bacteria and viruses, and hence provide a proper infection spread control. However, ozone generators are said to be not efficient enough in clearing the air from dust and mold, and hence manufacturers produce ozone air purifiers combined together with certain types of air filters in order to assure an effective indoor air cleaning. A biozone air purifier could be of greater efficiency in eliminating dust, pollen, mold and tobacco smoke from the air, when constructed with an ionizer. Even though there are a lot of advantages of ozone air purifiers in indoor air cleaning, there is a great concern of the effects of an ozone molecule on people’s health. It is well known that the exposure to high levels of ozone could be harmful to health and can irritate the respiratory system.

Biozone air purifier prevents respiratory diseases

The World Health Organization (WHO) states that high levels of ozone cause throat irritation and cough, decrease in lung function, chest pain, higher susceptibility to respiratory disease and aggravation of asthma. According to such data, there is a great controversy as to the safety of such biozone air purifiers for basic public use. However, there is no consensus to say when ozone levels become harmful to people. A few regulatory agencies, such as the Food and Drug Association (FDA) and the Occupational Safety and Health Administration (OSHA), have set their safety limits for exposure to ozone, based on the available facts. The FDA recommends that the concentrations of ozone should not exceed 0.05 ppm (parts per million) for continual exposure, while OSHA has set 0.1 ppm as a maximum for 8 hour exposure. The firstozone air purifier used to produce ozone levels over these recommendations. Some manufacturers of biozone air purifiers have presented ozone sensors, which shut off the units automatically when ozone levels reach a prescribed limit. These sensors are usually attached to such ozone generators. While this is a step in the right direction, the ozone sensors do not seem to work effectively in all size areas and cannot control high concentrations of ozone while working. In addition, due to excessive cost most manufacturers provide with models without ozone sensors.

Air cleaning methods

Passive air cleaning methods, such as media filtration, electrostatic precipitation and adsorbent materials are used in HEPA air filters . These methods may be combined with ultraviolet (UV) light or active air cleaning methods, such as negative ion generators or ozone generators , in order to increase the performance of HEPA air purifiers.

Air cleaning methods

The simplest technique is media filtration, which involves a filter most often made from an advance technology paper, textile, metal, synthetic, glass, or other material. The media filtration in a HEPA filter is made of submicronic glass fibers, that is as thick as blotter paper. As air is blown through the filter, usually with a blower attached to a motor, indoor allergens such as smoke, pollen, dust, mold spores, and bacteria, become trapped in the filter while the air flows freely through the filter. Harmful particles are eliminated from the air and the air that returns to the room is clean and fresh afterwards. The disadvantage of such cleaning method is that the air purifier needs a periodical filter replacement. The period of replacement is due to the amount of airborne particles that an air purifier is exposed to.

Another method used in HEPA air purifiers is electrostatic precipitation. It is based on high voltage electronics that charges airborne particles, so that they can be exposed to electrical forces within electronic cells. Electrically charged particles can then attach to a metal plate in the air purifier and remain there while the air is cleared from them. This type of an air purifier needs periodic cleaning of electronic cells with a special cleaner. While using either media filtration or electrostatic precipitation air purifiers the air in a facility should be cleaned at least 6 times per hour to eliminate all the existing allergens. The amount of times that the air should be cleaned depends on pollution of the area covered. It may rise from 8 to 10 times per hour and more in a highly contaminated area.

 

A more efficient method used in HEPA air purifiers than media based or electrostatic precipitation is adsorbent materials. A wide range of gaseous substances is eliminated from the air while adsorption. Different materials, such as activated carbon or charcoal, zeolite and alumina potassium permanganate are used for this purpose. Such HEPA air purifiers are used in areas full of gases, fumes, odors or other volatile organic compounds. In order to increase the efficiency of an air purifier, a combination of several methods is designed in HEPA air filters. This results in a rise in price. In general, the price of a HEPA air purifier depends on a size of a device, area coverage and the technique used.