Usually, unpleasant odors from the air conditioner appear after the equipment is turned on. Such a problem is encountered after a long downtime of equipment (for example, when the device did not turn on all winter), as well as for a number of reasons of a different nature. Before proceeding to the getting rid of unpleasant odors, it is necessary to find out the source of their occurrence.

The main causes of bad odors

In general terms, you can identify the root cause of the appearance of unpleasant odors literally by smell:

  • the persistent smell of plastic is typical for cheap split systems, the indoor unit of which is made of low-quality plastic; in the vast majority, such an aroma appears in the first days of operation of the air conditioner and disappears on its own over time; just in case, it is advisable to check that the case of the indoor unit does not melt in the heating mode;
  • the smell of burning can signify problems both with the internal components of the air conditioner and with burnt wiring; upon detection, you must immediately disconnect the device from the mains and call qualified specialists for further investigation; you should not ignore the smell of burning – it often leads to fires;
  • damp and moldy odors are due to the growth of the population of fungi and microbes in the ventilation system of the air conditioner; humid and warm environment in the indoor unit of air conditioning equipment – ideal conditions for the reproduction of pathogenic microorganisms;
  • the smell of dust is most often formed due to clogged filters that are located behind the front panel of the indoor unit; it also signals that pollution has reached the evaporator and fan of the indoor unit; dust aromas are most pronounced when the air conditioner is turned on for heating after long periods of inactivity;
  • the smell of sewerage when the air conditioner is turned on is formed due to the lack of a siphon for draining condensate or drying water in the siphon during long-term downtime of the climatic equipment; the problem is relevant only for the equipment, the installation of which is made with the drain of condensate directly into the sewer;
  • chemical odors can signal refrigerant leaks; so, the once popular freon R22 is characterized by a faint aroma of chloroform; more advanced types of refrigerants in high concentrations also "smell of chemical substances".
Good to know. What types of refrigerant air conditioning equipment works on is described in the article “What are the types of refrigerant in air conditioners”.

The main factor that leads to the formation of stench from the air conditioner are fungi and bacteria. Harmful microorganisms actively multiply in the heat exchanger of the indoor unit, the condensate collection tray, on the surfaces of the filters. A particularly ideal environment for them is liquid stagnation that occurs when the air conditioner is turned on rarely.

The main sources of unpleasant odors from the air conditioner are fungi, bacteria, mold and other harmful microorganisms.

Most of the air conditioning equipment works on the principle of air mass recirculation. The air conditioner in a circle passes through itself the same volume of air in the room. As a result, the device absorbs ambient odors such as perfumes, tobacco smoke, plastics and synthetics, animal odors, wet shoes, etc. A cocktail of odors is mixed and served back into the room. This problem is especially acute in rooms that have recently been renovated. Air conditioners with the function of fresh air intake are deprived of this flaw, however, not everyone can afford them because of the high cost of such equipment.

Air Conditioners with Fresh Air Intake

Getting rid of unpleasant odors

Drying the air conditioner and cleaning the indoor unit

Household air conditioners usually have a delayed fan off function. It continues to work for a while after the main mode is turned off, thus ensuring the dehumidification of the evaporator and tray. Some models do not have this option. The way out of the situation is to turn on the ventilation manually (ventilation mode without changing the temperature). It is enough to start the air conditioner in ventilation mode literally for 5 – 10 minutes after turning off the main mode.

Make it a rule to regularly wet clean the indoor unit of the air conditioner.

Dust and small particles constantly accumulate in the indoor unit of the air conditioner, which serve as a breeding ground for microorganisms. To remove them, you need to regularly clean the interior surfaces of the indoor unit. Lift the lid, remove the filters and inspect the interior, then gently clean the surfaces with a damp cloth and soapy water or a vacuum cleaner. To enhance the effect, you can use various antibacterial products.

Antibacterial treatment of air conditioner

Special antibacterial products are used to disinfect the air conditioner. Usually, such compositions are sprayed near the operating unit, switched to ventilation mode. It will take only 10-15 minutes to disinfect the evaporator and the working area. During this period of time, a resistant protective film is formed on the internal elements of the unit, which further prevents the growth of microorganisms and the formation of unpleasant odors. Flowing down, the remnants of antibacterial products additionally disinfect the tray. Filters can also be treated with similar products.

There are many antibacterial sprays in stores for disinfection of the indoor unit of the air conditioner.

Cleaning the drainage system

Often in air conditioners, the drainage system becomes clogged. The problem is solved by cleaning the condensate drain hole in the indoor unit from dirt and blowing the drain pipe (for example, using a vacuum cleaner). With dense blockages, specialized cleaning products will help, which are poured into the tube with an standard syringe.

At the end of the cleaning procedure, it is desirable to disinfect the drainage system. The condensate collection tray and the condensate drain tube can be treated with the above-mentioned disinfectants. Also, chlorhexidine, sold in any pharmacy, will fit this role.

The drainage system of the air conditioner requires attention and needs to be periodically cleaned of contaminants.

If none of the above helps, the drain may need to be redone due to improper installation of the air conditioner.

Use of specialized filters and their timely cleaning

The work of specialized filters is aimed at neutralizing many unpleasant odors. Filtration systems in modern air conditioners not only trap dust and large particles of contaminants, but also perform high-quality air cleaning. The following types of filters do a good job of eliminating unpleasant odors:

  • Plasma (electrostatic) – this type of filter is often called plasma ionizers. Their action is based on the saturation of the air with negatively charged particles, which is ionization. Plasma filters effectively destroy microorganisms, trap dust and soot particles – under the influence of ionized air flows, such particles acquire a charge and are attracted to the filter plates.
Air Conditioners with Plasma Filter

  • Catalytic – decompose any odors of organic origin due to a special substance (photocatalyst) and UV radiation. The technology allows to remove harmful impurities from the air (at the level of individual molecules), while simultaneously providing a good bactericidal and antiviral effect. Catalytic filters do not need to be replaced as they regenerate themselves under UV rays. There are also air conditioners with a built-in UV lamp.
Air Conditioners with Catalytic Filter

  • Deodorizing (carbon) – the main task of these filters is to neutralize unpleasant odors. Deodorizing filters use sorbents (usually activated carbon). The air passes through them freely, together with which it is cleared of harmful impurities and odors. Since sorbents absorb and accumulate pollution, the working element of such filters must be changed periodically (about once every six months). When the resource is exhausted, it becomes useless and even releases harmful substances itself.
Air Conditioners with Deodorizing Filter

  • Antibacterial and antifungal – a group of filters for the destruction of harmful microorganisms, which often cause unpleasant odors from the air conditioner. Antibacterial filters provide a clean and healthy microclimate.
Air Conditioners with Antibacterial Filter

  • Catechin filters are a special kind of antibacterial filters with the active substance catechin. It is a natural component for effective air disinfection. Usually catechin filters are purchased separately, and they are very expensive.
Visualization of the catalytic filter operation – air cleaning with its help is carried out due to a special substance – photocatalyst and UV radiation.

Excessive dustiness of the filters cause not only the appearance of unpleasant odors, but also a decrease in the generation of cold. Filters must be cleaned periodically. Usually it is enough to remove them from the indoor unit, rinse in warm water and dry thoroughly. For specialized filters, it is better to look in advance for the care rules in the technical documentation.

Details about filtration systems in air conditioning equipment are described in the article “Clean and healthy air! Types of filters in air conditioners.

Siphon installation

When connecting an air conditioner with condensate drainage to the sewer, it is important to use a siphon, which is introduced into the drainage scheme exactly to eliminate unpleasant odors. Without a siphon, all the odors from the sewers easily penetrate into the apartment. However, even with a siphon, odors sometimes make their way into the room from sewage. This occurs when the air conditioner is idle for a long time – the water in the siphon evaporates and unpleasant odors pass through it. The problem will be solved when the entire volume of the siphon is filled with condensate again.

In schemes with condensate drainage to the sewer, a siphon must be installed.

Regular preventive maintenance and service

Regular preventive maintenance and service are important factors in the operation of any air conditioner. Preventive cleaning is recommended to be performed every six months, and maintenance is carried out according to the regulations of the air conditioning equipment manufacturer – it is customary to call specialists to inspect equipment and refill it with refrigerant every two or three years. This not only prevents unpleasant odors, but also guarantees best air conditioning performance.


If you are choosing air conditioning equipment, we recommend that you first read the article “How to choose an air conditioner”.