Main types of filtration and mechanical air cleaning in split systems

Air Filtration Systems in Air Conditioners

The air filtration function in an air conditioner represents an integrated multi-stage cleaning system aimed at removing a wide range of contaminants from the airflow. Depending on the design, it may include mechanical, carbon, antibacterial, and high-efficiency HEPA filters, providing retention of dust, pollen, mold spores, microscopic particles, bacteria, and viruses. Effective filtration significantly improves indoor air quality, reduces the risk of allergic reactions and infection spread, protects the internal components of the air conditioner from contamination preventing premature wear, and contributes to increased energy efficiency by allowing free air passage and reducing system load.

Types of Filters in Air Conditioners

Filters in residential air conditioners are conventionally divided into two types: standard and additional. Standard filters serve to protect the internal components of the device from dust and large contaminants, while additional filters aim to improve indoor air quality.

The standard filter is a mechanical coarse mesh. It traps a significant amount of large particles such as dust, hair, lint, and insects. Its main function is to protect the heat exchanger and other air conditioner parts from clogging and breakdowns.

Additional filters are mounted over the mesh and include various types:

• Carbon;
• Antibacterial (including catechin and silver ion filters);
• Biofilters (including enzyme and plant extract based);
• Vitamin-enriched filters;
• Multifunctional (combined) filters;
• Photocatalytic and plasma systems;
• Ultraviolet lamps;
• HEPA filters.

1. Mechanical Coarse Filters

The standard mesh filter is made from polypropylene fibers or metal mesh with cell sizes of 0.5–2 mm. Its main function is protecting internal air conditioner components from:

• Coarse dust particles (50–1000 ?m)
• Animal hair
• Plant pollen
• Insects

2. Carbon (Adsorption) Filters

These consist of plates or cartridges with activated carbon of various structures:

• Granulated carbon (granule size 0.5–3 mm)
• Powdered carbon (applied on polymer base)
• Modified carbons (with alkali metal salt additives)

Effective against gaseous pollutants such as volatile organic compounds, household odors, formaldehyde.

3. Antibacterial Filters

Include several technological variants:

• Catechin-based: containing polyphenolic compounds from tea extract
• Silver-ion: using silver nanoparticles sized 10–100 nm
• Enzymatic: based on immobilized enzymes (lysozyme, glucose oxidase)
• Wasabi filters: containing isothiocyanates from Japanese horseradish

4. Photocatalytic Systems

Consist of three key components:

1. Catalyst (titanium dioxide TiO₂ in anatase form)
2. Ultraviolet emitter (wavelength 365 nm)
3. Porous substrate (ceramic or fiberglass)

Effective against viruses, bacteria, and volatile organic compounds.

5. Electrostatic (Plasma) Filters

Operate on the principle of corona discharge (voltage 5–15 kV) between electrodes. Capture:

• Aerosol particles (0.01–1 ?m)
• Bacteria and viruses
• Tobacco smoke

6. HEPA Filters

Used in air conditioners in three classes:

7. Combined Filtering Systems

Multilayer constructions combining:

• Preliminary mechanical layer
• Adsorption layer (carbon)
• Antimicrobial impregnation
• Final HEPA barrier

Evaluation of Air Filtration Effectiveness in Air Conditioners

The efficiency of air purification in air conditioners depends on the filter surface area and airflow velocity. Standard filters trap large particles but cannot clean the air from fine particulate matter such as PM2.5 and PM10, which are most hazardous to human health. These particles easily penetrate the respiratory tract and can cause respiratory diseases and allergies.

Additional filters vary significantly in mechanism and effectiveness. Carbon filters partially remove odors but cover only a limited portion of airflow and contain a small amount of active substance, reducing their effectiveness. Filters with antiseptic additives (catechin, silver ions, wasabi extract) have disinfectant properties but are also limited in real-world efficiency due to their size.

Photocatalytic and plasma filters can remove microorganisms and harmful gases, but efficiency depends on air contact time with the active surface. High pollutant concentrations may lead to intermediate oxidation products potentially harmful to humans. Ultraviolet lamps in air conditioners are applied locally and do not cover the entire volume of air passing through the device, limiting their usefulness.

HEPA filters, although recognized as a fine purification standard, are used only partially in air conditioners. Due to their small surface area and partial airflow coverage, they do not achieve the filtration level typical for specialized air purifiers.

Air Conditioner Capabilities in Maintaining Air Cleanliness

Air conditioners, even with additional filters, cannot replace fully functional air purifiers. Their filtration elements are not designed to remove all types of pollutants, including aerosols, allergens, and harmful gases. They perform conditioning functions and partially improve air quality but do not provide deep cleaning.

Some filters, such as photocatalytic and plasma, can reduce virus and bacteria concentrations. However, they do not remove dust, allergenic particles, and fine pollutants, which are the main causes of indoor air quality deterioration.

Cleaning the Air Conditioner Air Filter

The air filter should be cleaned after 100 hours of operation or after the symbol appears on the remote control display.

The cleaning procedure is as follows:

Turn off the air conditioner.
• Open the front panel.
• Gently pull the filter lever towards you.
• Remove the filter.

Cleaning and Reinstalling the Air Filter

After cleaning, thoroughly dry the filter.

Install the filter back into place.

Close the front panel again.

(!) NOTE
Wash the air filter every two weeks if the air conditioner operates in a heavily polluted environment.

The Role of Supply Ventilation in Maintaining Air Quality

For a comprehensive solution to air pollution problems, installation of a supply air purifier (breather) is recommended. The breather supplies purified outdoor air filtered through:

• Pre-filter — for coarse cleaning;
• HEPA filter — for fine cleaning and removal of PM2.5 and PM10;
• Carbon or photocatalytic filter — for odor, bacteria, and harmful gas removal.

The breather also controls indoor carbon dioxide levels by active air exchange. Thus, not only filtration but also air composition normalization is achieved, including reducing pathogenic microorganism concentrations.

The combination of an air conditioner and supply ventilation provides a comfortable microclimate: the breather supplies purified air, and the air conditioner regulates its temperature. This tandem is an optimal solution for cleanliness and comfort in living spaces.

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iFAVOR Function in Air Conditioners
TIMER Function in Air Conditioners
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Automatic DEFROST MODE Function
AIR Fresh Air Supply Function
Automatic AUTO Mode