Air filter: The guardian of air purification

In the environment where we live, the air is filled with all kinds of impurities, such as dust, pollen, bacteria, viruses and harmful gases, etc. These pollutants not only affect our respiratory health, but may also cause damage to some devices. Air filter, as important equipment for purifying air, play a crucial role. This article will delve deeply into the relevant knowledge of air filters, including their working principles, types, application fields, as well as maintenance and future development trends. ​

1. Working principle

The working principle of air filters is mainly based on mechanisms such as interception, adsorption and electrostatic attraction. When air containing pollutants passes through the filter, the filter medium of the filter will intercept particulate pollutants of different sizes. For instance, larger dust particles can be directly intercepted by the pores of the filter medium, while smaller particles may collide with the filter medium through Brownian motion and other means and be adsorbed. Some advanced air filters also utilize the principle of electrostatic adsorption. By applying static electricity to the filter medium, charged pollutants are more easily adsorbed onto the filter medium, thereby enhancing the filtration efficiency. ​

2. Type

Classified by filtration efficiency

Primary filter: Mainly used for filtering dust particles larger than 5μm, it is suitable for the primary filtration of air conditioning systems, such as pre-filtration in central air conditioning and centralized ventilation systems, and pre-filtration in large air compressors, etc. The primary filters come in three styles: plate type, folded type and bag type. The outer frame materials include paper frame, aluminum frame, galvanized iron frame, etc. The filter materials include non-woven fabric, nylon mesh, etc. Its features include low cost, light weight, good versatility, compact structure, the ability to replace filter materials by oneself (the primary effect of the paper frame is disposable), low resistance, large air volume and long service life. ​

Medium-efficiency filters: Mainly used for capturing particles of dust and various suspended substances ranging from 1 to 5μm, they can be applied in central air conditioning centralized ventilation systems or serve as pre-filters for high-efficiency filters to reduce their burden and extend their service life. They can also be used for general air purification in industrial fields. The frame of the medium-efficiency filter is available in forms such as cold-rolled steel plate with plastic coating and galvanized steel plate, and the filter materials include non-woven fabric and glass fiber. The bag-type medium-efficiency filter has low resistance and large dust holding capacity. The folding medium-efficiency filter features high efficiency, large dust holding capacity and small space occupation.
​
High-efficiency filter It is divided into pleated high-efficiency filters and non-pleated high-efficiency filters, mainly used for capturing fine particles ranging from 0.1 to 0.5μm. It is suitable for clean air conditioning systems and high-cleanliness environments. It is used in industries such as microelectronics, precision instruments and meters, medical and health care, bioengineering, pharmaceuticals and food, as well as in the final stage of air filtration in various clean rooms, clean tunnels, high-efficiency air supply outlets, clean workbenches, air showers and other purification equipment. This product is precisely crafted through a strict process, featuring ultra-fine glass fiber filter material, hot-melt adhesive as the separator, special aluminum profile outer frame, polyurethane two-component sealant, closed-cell sponge sealing strip, and powder-coated steel mesh flow distribution plate. It is characterized by high efficiency and low resistance. ​

Sub-high efficiency filters: They are used for terminal filtration in various clean projects and central air conditioning and process air supply systems with special requirements, as well as for filtration in clean rooms. They feature high filtration efficiency, low resistance, and large dust holding capacity. ​

(2) Classification by filter material

Paper filters: such as paper dry air filters, whose filter elements are made of resin-treated microporous filter paper, are often used in fields like automotive engines. Its advantages are lightness, low cost, high filtration efficiency and easy maintenance. ​

Fiber filter: It uses fiber materials as the filtering medium, such as glass fiber, synthetic fiber, etc. Fiber filters have a good filtering effect on fine particles and are widely used in some industrial and medical fields with high requirements for air quality. ​

Activated carbon filter: By taking advantage of the highly developed microporous structure of activated carbon, it effectively removes odors, volatile agents, bacteria, viruses and various air pollutants, such as paint spray and smoke. It is often used in food processing plants, hospitals, museums and other places with high requirements for air odor and pollutant control. The use of activated carbon filtration must have a pre-filter; otherwise, the efficiency of activated carbon will be reduced due to other pollutants in the air. ​

Polyurethane filter element filter: Made of sponge-like polyurethane, it has strong adsorption capacity but relatively low mechanical strength. It is mostly used in equipment such as cars where there are certain requirements for the volume and weight of the filter. ​

3. Application fields

(1) Residential field

In households, air filters can be installed in equipment such as air conditioners and fresh air systems. As people's attention to indoor air quality keeps increasing, air filters play a crucial role in improving indoor air quality. For instance, for families with people suffering from allergies or respiratory diseases, choosing the right air filter can effectively filter out allergens such as pollen, dust mites and bacteria, thereby alleviating the symptoms of the patients. Different family needs can choose filters of different MERV (Minimum Efficiency Reported Value) grades. Generally, families can choose filters of MERV grade 11, which is moderately priced and can meet the needs of typical families. For families with severe allergies or respiratory sensitivity problems, it may be necessary to choose filters of MERV 13 or above grade. ​

(2) Commercial building field

Office buildings: The application of advanced office equipment, such as computer terminals, inkjet printers, dry photocopiers, fax machines, laser printers, etc., will generate pollutants such as ozone, volatile organic compounds, hydrocarbons, and inhalable suspended particles, seriously polluting the indoor environment. It is estimated that 30% of office buildings and public buildings in the United States have indoor air pollution problems. Therefore, office buildings need to install air filters to improve air quality and protect the health of personnel and office equipment. For example, in order to improve the air quality, the hall of Chicago D 'Hare Airport is equipped with a total of 1,100 pre-filters, 1,100 final filters and 2,200 carbon filters (among which the carbon needs to be replaced every 10-12 months). ​

Shopping malls, hotels, etc. : These places are crowded with people and have a large volume of air circulation, making it easy for various pollutants to accumulate. Installing air filters can keep the indoor air fresh, enhance the comfort of customers and employees, and also help reduce the spread of bacteria and viruses, safeguarding public health. For instance, installing high-efficiency air filters in hotel guest rooms and public areas can effectively filter out odors and microorganisms in the air, providing guests with a comfortable accommodation environment. ​

(3) Industrial field

The food industry: The demand for air filtration equipment in the food industry is constantly increasing. To maintain the fresh taste of food, reduce the use of chemical preservatives, and control air pollution related to products has become even more important. For instance, in Europe, yogurt canning is carried out under cleanroom conditions. By using a top ventilation system and HEPA filters for filtration, the product can be preserved for a relatively long time without the addition of expensive chemical preservatives. To protect draft beer, breweries need to control the air pollution around the filling workshop. They usually adopt 100,000-grade clean rooms and use HEPA filters. ​

The electronics industry: The electronics industry has extremely high requirements for the air quality of the production environment. Even tiny dust particles can have a significant impact on the production and performance of electronic components. Therefore, in workshops such as electronic chip manufacturing and electronic equipment assembly, high-efficiency or even ultra-high-efficiency air filters need to be used to ensure the cleanliness of the production environment, improve product quality and production efficiency. ​

Pharmaceutical industry: The pharmaceutical process must be carried out in a strictly controlled clean environment to prevent the contamination of drugs by microorganisms and dust particles. Air filters are widely used in the air conditioning systems, clean rooms and other links of pharmaceutical workshops to ensure that the production of drugs meets strict quality standards and guarantee the safety and effectiveness of drugs.
​
(4) Medical field

Hospitals: Hospitals are places where various bacteria and pollutants are concentrated. To prevent cross-infection and ensure the health of patients and medical staff, high-performance air filters need to be installed in all areas of the hospital, such as operating rooms, wards, and intensive care units. In the operating room, high-efficiency air filters are usually used to filter out bacteria, viruses and other microorganisms in the air, creating a nearly sterile surgical environment and reducing the risk of surgical infection. The air filters in the ward can filter out germs in the air, providing patients with a clean rehabilitation environment. ​

Laboratories: Research laboratories also have very high requirements for air quality, especially those that conduct experiments such as microbial research and cell culture. Air filters can prevent external contaminants from entering the laboratory, ensuring the accuracy and reliability of the experimental results. For instance, in a biosafety laboratory, special high-efficiency air filters need to be used to ensure that the air inside the laboratory does not cause pollution to the environment when it is discharged. ​

(5) Transportation field

In a car, the air conditioning filter can filter the air entering the vehicle, removing pollutants such as dust, pollen, and harmful gases, providing a clean air environment for passengers inside. Especially on urban congested roads, where vehicle exhaust emissions are large and air quality is poor, the role of on-board air filters becomes even more prominent. As mentioned earlier, the Philips GoPure high-quality in-car air filter has multiple functions and can effectively improve the air quality inside the vehicle. ​

Aircraft: The air in the aircraft cabin needs to undergo strict filtration and circulation treatment to ensure that passengers can breathe clean and healthy air during the long flight. The air filters on the aircraft can filter out microorganisms, dust particles and odors in the air, providing passengers with a comfortable flying environment. At the same time, air filters are also installed in the aircraft's engine intake system to protect the engine from damage caused by impurities in the air and ensure the normal operation and performance of the engine. ​

4. Maintenance and replacement

(1) Maintenance key points

Regular inspection: Regularly check the appearance of the air filter to see if there is any damage, blockage or other conditions. For washable filters, it is necessary to check the effect after cleaning to ensure that the filter medium is not damaged. For filters installed in important equipment such as central air conditioning and industrial production equipment, regular inspections are particularly important to ensure the normal operation of the equipment. ​

Keep clean: For the outer frames and peripheral components of some filters that are prone to dust accumulation, regular cleaning should be carried out to prevent dust from being sucked back into the air circulation system. During the cleaning process, be careful not to cause damage to the filter itself. ​

Pay attention to the operating environment: Understand the applicable environmental conditions of the air filter, such as temperature, humidity, pH value, etc. Avoid installing the filter in an environment beyond its applicable range to prevent affecting the filtration effect and service life. For instance, ordinary air filters may age and get damaged more quickly in environments with high temperatures, high humidity or corrosive gases. ​

(2) Replacement cycle

The replacement cycle of air filters varies depending on the usage environment and the type of filter. Generally speaking, for air conditioning filters used in residences, if the home environment is relatively clean and there are no pets or smoking, they can be replaced every 3 to 6 months. If there are pets at home, smoking or the air quality in the area is poor, it is recommended to replace it every 1 to 3 months. In the commercial and industrial fields, due to the large air circulation volume and high pollutant concentration, the replacement cycle of filters is usually shorter. For example, the high-efficiency air filters in hospital operating rooms may need to be inspected and replaced monthly or even weekly. The replacement cycle of air filters in factory workshops may range from a few days to several weeks depending on the production process and the degree of pollution. To facilitate users to replace the Filters in a timely manner, some manufacturers have also launched Smart Air filters, such as Filtrete™ Smart Air Filters. These filters monitor the air flow and usage through sensors and remind users when the filters need to be replaced.

5. Future Development Trends

Higher filtration efficiency

As people's demands for air quality continue to rise, air filters will develop towards higher filtration efficiency in the future. R&d personnel will continuously explore new filtration materials and technologies to achieve effective filtration of smaller particle pollutants (such as nanoscale particles) and a wider variety of pollutants (such as emerging harmful chemicals). For example, research on new types of nanofiber materials, which have finer pore structures and can intercept tiny particles more precisely; Or develop materials with multi-functional adsorption properties, which can not only filter particulate matter but also simultaneously remove harmful gases and microorganisms. ​

(2) Intelligent development

Intelligence is one of the important development trends for air filters in the future. Intelligent air filters will be equipped with more sensors and intelligent control systems, which can monitor air quality and the working status of the filters in real time, and automatically adjust the filtration mode and remind users to replace the filters according to the actual situation. By connecting with the smart home system, the smart air filter can also achieve remote control and automated management, providing users with a more convenient and efficient air purification experience. For instance, users can check the operation status of the air filter at home anytime and anywhere through a mobile phone APP, set the filtration parameters, and even turn on the air filter in advance before returning home to create a fresh indoor environment for themselves. ​

(3) Energy conservation and environmental protection

Under the global advocacy of energy conservation and environmental protection, air filters will also focus on reducing energy consumption and minimizing their impact on the environment. On the one hand, by optimizing the structural design of the filter and the air flow channel, the resistance of air passing through the filter is reduced, thereby reducing the energy consumption of air conditioning, ventilation and other equipment. On the other hand, develop recyclable and degradable filter materials to reduce the pollution to the environment caused by the disposal of filters. For instance, using biodegradable fiber materials to make filter media, when the filter reaches the end of its service life, it can decompose in the natural environment and will not cause long-term environmental pollution like traditional plastic filters. ​

(4) Multi-functional integration

Future air filters will not only be limited to filtering particulate matter and microorganisms, but also integrate more functions, such as removing harmful gases, regulating air humidity, and releasing substances beneficial to health (such as negative oxygen ions), etc. Through multi-functional integration, air filters can provide users with more comprehensive and high-quality air purification services, meeting people's diverse demands for a healthy and comfortable indoor environment. For instance, some air filters have begun to integrate activated carbon layers to adsorb harmful gases. In the future, the performance of activated carbon may be further optimized and combined with other technologies to achieve efficient removal of various harmful gases. Meanwhile, by adding a humidity regulation module and a negative oxygen ion generator, the air filter is endowed with the functions of regulating air humidity and improving air quality, creating a fresh and comfortable indoor environment similar to a forest for users. ​

Air filters play an indispensable role in all aspects of our lives, from safeguarding our respiratory health to ensuring the smooth operation of industrial production. With the continuous advancement of technology and the increasing attention people pay to air quality, air filters will keep innovating and developing to create a cleaner and healthier air environment for us. Whether in a home, an office or an industrial plant, choosing the right air filter and carrying out correct maintenance and replacement are the keys for us to enjoy fresh air.