Types of Filters in Air Purifier & Air Conditioner

May 10, 2021

Air pollution is growing at an alarming rate, globally. No matter where we are, the air around us is no longer completely free of dust and smoke. It contains harmful chemicals and microorganisms that have the potential to make us seriously ill.

As the causes of air pollution continue to rise, people in urban areas are increasingly turning to air purifiers and air conditioners to secure their living spaces.

These appliances remove microscopic pollutants from the air and make it safer for respiration. In this article, we are going to learn about the different filters used in air purifiers and air conditioners. We will study how they are made and their uses.


What is an air filter ?

An air filter is a device made of porous or fibrous materials which trap solid, liquid and gaseous particles suspended in the air. The particles can be living or non-living, organic or inorganic.

They can have diameters of less than a micron (micrometer) to more than a hundred micron. Air filters are used in home and car air purifiers.

An air filter can be active or passive. An active air filter directly acts upon air pollutants, and destroys or de-activates them. The best air purifiers in the market use a combination of active and passive methods to purify air.

MERV Rating :

Before we discuss the different types of air filters, it is imperative that we talk a little bit about MERV rating. It was conceptualized and developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). The following table shows the MERV ratings for different particle sizes.

MERV rating   Minimum particle size (in micron) Pollutants intercepted Applications:

1 to 4, 10.0 micron: fabric fibers, dust, pollen, sand, spray paint dust HVAC units
5 to 8, 0–3.0 micron: spores, pet dander, dust mites, dust mite feces, aerosol mist HVAC units
9 to 12, 3.0–1.0 micron: vehicular smoke, lead dust, humidifier dust, particulate matter HVAC units in hospitals and sensitive work places
13 to 16, 1.0–0.3 micron: bacteria, particulate matter, most smoke, most paint pigments, cooking oil droplets Operation Theatre, Intensive Care Unit
17 to 2, 0 < 0.3 micron: smoke, bacteria, viruses, carbon dust Electronics, pharma labs, cleanrooms, pathology research centers

Types of Filters in Air Conditioners :

Electrostatic air filter

An electrostatic filter is based on the principle of static electricity. When air molecules rub against the filter medium, it produces friction which makes the air pollutants present in the air current adhere to the filter.

Uses of electrostatic filter :

Electrostatic filters are widely used in air purifiers and air conditioners. They are instrumental in rooting out positively charged particles like pollen, fungal spores, dust mites, pet hair and lint. A typical filter can last for years if maintained well.

Nano silver filter

Nano silver filters are used for inhibiting bacteria. Silver is known for its anti-microbial quality and nano silver filters harness this quality if silver to counter bacterial growth.

Uses of nano silver filter :
Nano silver filters are used in home air conditioners and air purifiers. They can neutralize up to 600 different kinds of bacteria.

Pleated air filters

Pleated filters are a more advanced version of fiberglass filters. They are a step up from fiberglass filters with a higher airflow resistance. They trap more particles than fiberglass filters and protect the inner filters.

Uses of pleated filters :

Pleated air filters are used in both furnace and HVAC systems. They are built into air purification units and air conditioners.

They usually have a MERV rating of 10 to 13. They are suitable for people with skin allergies and respiratory disorders like asthma. Pleated filters are more expensive than fiberglass filters.

Filters in Air Purifiers:

HEPA Filter:

HEPA stands for High-Efficiency Particulate Arresting (or Absorber). It is the only filter that can remove particles as small as 0.3 micron. It has a high filtration rate. It can eliminate up to 99.97% airborne allergens from an enclosed area.

Uses of HEPA filter:

HEPA filters are predominantly used in domestic and industrial air purifiers, vacuum cleaners and air conditioners. They are used in aircraft air purification systems to prevent the spread of germs in re-circulated cabin air.

They are also used in biomedical applications to fight bacterial and viral infections. HEPA filters are allergy and asthma-friendly. They help check allergic reactions and asthmatic attacks.

Portable hepa air filters are a great alternative to expensive and bulky hepa filters. A portable filter can be a life-saver if you have allergies or asthma and need a quick fix. These devices are convenient, cost-effective, and easy to use.

Activated Carbon Filter:

Activated carbon filter for air filtration

Activated carbon is carbon that has been treated with jets of hot air, steam or carbon dioxide in order to increase its surface area and makes it more porous. Treating carbon in this manner makes it perfect for trapping organic gaseous and liquid particles present in the air.

Carbon already occurs naturally in the form of a web or trellis of inter-connected carbon atoms. When jets of air and steam are passed through it, millions of tiny pores develop between the carbon atoms, increasing the surface area of the metal exponentially.

When air is passed through an activated carbon filter, the organic particles suspended in the air stick to the surface of the carbon atoms and are separated from the air stream.

Uses of activated carbon filter :

Activated carbon removes unpleasant odors, cooking smells and toxic gases. Most importantly, it removes VOCs. VOCs are a group of chemicals released by household products like cleaning supplies, paints, adhesives, polythene bags, deodorants, synthetic fabrics, scented personal care products and plywood furniture.

Examples of VOCs are formaldehyde, ammonia, benzene, toluene, xylene and acetone.

Activated carbon filters are used in air purifiers, air conditioners, kitchen exhaust systems and vacuum cleaners. They are used in domestic and industrial applications in a wide range of sectors like consumer appliances, pharmaceuticals, FMCG, automobile and chemical plants.

Activated carbon filters are recommended for people with Multiple Chemical Sensitivity (MCS).

Ultra Violet (UV) light Air filter :

UV light is a part of the electromagnetic spectrum with a wavelength of 10 to 400nm (nano meter). It lies between visible light and X-Rays. It is shorter than visible light and longer then X-rays.

UV light is hotter and has more energy than visible light. It cannot be seen with the naked eye but is extremely powerful. It is mutagenic to living microorganisms like bacteria and actively destroys allergens.

UV light can be classified into 3 main types: UV-A, UV-B and UV-C light. The first two types are emitted by the sun and are harmful for humans. They can cause sun burns, allergies and cancer of the skin.

The third type, UV-C light, doesn’t harm humans, but is fatal for living microorganisms. It is used in air purifiers for killing germs and sanitizing air.

UV lamps become less effective with use. Their efficiency goes down by an average of 15% annually.

Uses of UV light Air filter :

UV light is used for sterilizing germs in sterile work places like hospitals. It is commonly used in domestic and industrial HVAC (heating, ventilation and air conditioning) systems.

It plays a central role in practically every major industry including pharmaceutical, healthcare, nuclear power, microbiology, biotechnology, food & beverages, and chemical.

Studies have found UV light to be extremely effective in controlling the spread of infections in intensive care units in hospitals.

It has also proven to be highly effective in fighting fungal contamination in air handling units. UV light is perfect for humid climates as it fights mould. It also controls bad odors and VOCs.

Ionic Air Purifier or Ionizer :

Air ionizer

An ionizer is a device that relies on electrostatic energy to control air pollution. It is used for countering dust, bacteria, cigarette smoke and pet dander. It actively targets air pollutants and inhibits their growth by neutralizing them.

Uses of an ionizer :

Ionizers are commonly sold as ionic air purifiers. Hospitals and pathology laboratories use ionic air filters to combat bacterial growth and contagious diseases. Studies have found ionizers to be effectual in lowering salmonella outbreaks and other air-mediated infections.

Photo Catalytic Filter :

Photocatalytic filter

It eliminates VOCs, vehicular fumes, cooking smoke and other allergy-inducing particles.

Hydroxyl radicals are highly volatile and reactive. They react with large carbon-based pollutants and convert them into harmless compounds like carbon dioxide and water. In other words, the filter permanently alters the chemical composition of organic pollutants, transforming them from harmful to harmless particles.

Uses of photo catalytic filter :

PCO filters are used in all kinds of air purification systems. They have a wide range of domestic and industrial applications.

Catechin Filter 

Catechin Air Filter

Catechin is a naturally occurring phenol and antioxidant found in tea, cocoa and pome fruits like apple. It has anti-bacterial and anti-viral properties. It destroys bacteria and prevents foul odors.

Uses of catechin filter:
They are washable, reusable and long-lasting.

Vitamin C filter:

Vitamin C plays a key role in the synthesis of collagen and elastin, both of which are vital for healthy glowing skin. Vitamin C moisturizes the skin and keeps it soft and supple.

Uses of vitamin C filter:
Vitamin C air filters can be seen in home and car air conditioners. They are also used in air purifiers for keeping the skin hydrated.

Anti-bacterial Filter:

Anti-bacterial air filters inhibit microbes like bacteria, viruses, spores and pollen. They are used to control the spread of germs and diseases.

Uses of anti-bacterial filter:
Anti-bacterial air filters are widely used in HVAC systems, furnaces, air purifiers and car air conditioners. They are installed in sterile work places like intensive care units, operation theaters, pharmaceutical plants and laboratories. A standard anti-bacterial filter lasts 3 to 6 months after which it needs replacement.


A pre-filter is the first filter the air goes through when it enters an air purifier. It does the preliminary screening, taking out large particles like human air, fur, pet dander, pollen, dust and sand.

It mostly tackles PM 10 contaminants and prevents them from getting to the inner, more expensive, filters like HEPA. The pre-filter prolongs the life of the other filters in the appliance and maintains the efficiency of the machine. It keeps the advanced filters from getting clogged with coarser debris and helps them perform at their most optimal levels.

There are 2 main types of pre-filters:

  • Fiberglass filter
  • Pleated filter

Fiberglass Filter:

Fiberglass filters are used for removing large debris like lint, sand, dust, and human and animal hair. They are cheap and disposable air filters. They can be purchased in department and hardware stores.

Uses of fiberglass filters:

Fiberglass filters are used in domestic and commercial furnaces and HVAC systems. They intercept larger particles before they could get to the inner, more sophisticated, filters.


You do not need to be confused as this article will give a clear difference between an air purifier and an air conditioner and the distinct function of the two entities, the advantages of using one or combination of both.

Air purifiers are majorly used for health reasons. An air purifier helps in removing the pollutants that can cause health problems in your room such as dust, smoke, bacteria and more.

Does Air Conditioner Purify Air

Air conditioners are majorly used for comfort purposes. They ensure that warm air or heat is being replaced with cooler air. Air conditioning unit has been misunderstood as a cleaning system which is not supposed to be so.

Air conditioning alongside with an air filter can carry out the function of cooling the room or office as well as providing an atmosphere free of contaminants.

Carlos Diaz
I believe in making the impossible possible because there’s no fun in giving up. Travel, design, fashion and current trends in the field of industrial construction are topics that I enjoy writing about.

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