Air purifiers – what to pay attention to?

Polluted air is the basis of many respiratory diseases and worsening of the well-being. We’re not talking only about smog here – some chemical compounds, allergic plant pollen, mold spores or simply dust may hinder everyday functioning. The easiest methods to deal with the pollutants that eventually get into our body along with the inhaled air are filter plants and air purifiers. If, for various reasons, we decide on the second solution, we will have to dig through a whole lot of possibilities – there are already hundreds of air purifiers on the market. What’s more, it’s impossible to clearly point to the best one. Everything depends on individual needs. In this article, therefore, we will not give a ready solution, but explain what to look for before buying an air purifier.

Firstly – how do air purifiers work?

Contrary to appearances, air purifiers are based on a very simple assumption. Such a device is designed to push air through the filter (or a series of filters) so that the vast majority of impurities will stop on it and not return to circulation. It is best, of course, if the purifier filters the largest volume of air in the shortest possible time. Its performance in this matter will be determined by the so-called CADR (Clean Air Delivery Rate), or the number of cubic meters of air that will be filtered in an hour. When comparing air purifiers, it should be borne in mind that they should be able to filter the air in a given room at least once an hour (good cleaners do it 3 times).

air purifiers

However, it should be remembered that one device will effectively clean the air in only one room. Unfortunately, the purifier placed in the bedroom won’t effectively cope with the polluted air from the kitchen on the opposite side of the apartment. Therefore, by adjusting the performance of the device, the volume of individual rooms should be calculated. Of course, not everyone can (and wants to) afford to buy several devices for one apartment. Air purifier should therefore be placed where we spend the most time during the day. In most cases, it will be a bedroom.

Types of filters for air purifiers

When choosing air purifiers, in addition to efficiency, we need to keep in mind what pollution disturbs us most. It will determine what type of filter we need in the device.

The basis of all equipment of this type is the purification of relatively large solid particles, i.e. dust, mold spores, pollen, animal hair, or PM10 and PM2.5 (the main components of smog in cities). In addition to the so-called pre-filter, which retains the largest dirt, there are two main types of filters:

Mechanical, i.e. nonwoven

These filters are nothing more than densely woven fibers (usually cotton or polyester), on which particles suspended in the air stop. If we want to buy a really effective purifier, basically the only filters worth attention are the so-called EPA and HEPA (High Efficiency Particulate Air). They ensure effective capture of over 99% of particles with a diameter of 0.3 µm. Smaller ones are also captured, but with slightly lower efficiency. Be aware, however, of the “HEPA-type” filters – their effectiveness may vary. Most often, HEPA filters in air purifiers have the “H13” designation – that is, they retain 99.95% of contaminants – and this is quite enough at home.

dust in the air

Of course, there are filters that operate with 99.999995% accuracy. However, the efficiency of the filters is related to the density of the fibers, which translates into the resistance that the air flowing through them must overcome. This in turn has consequences for the device’s efficiency and electricity consumption. It may turn out that, in theory, a slightly less effective EPA 12 filter (99.5%), in the same unit of time, will filter more m3 of air – therefore it will be much more suitable for our needs than filters with denser fiber.


Air purifiers with electrostatic filters, although slightly less popular, have many advantages. Filtration in electrostatic precipitators takes place in two stages. First, the polluted air flows through the electric field generated in the device. In this way, positively charged particles (suspended dust, dust, etc.) go to the oppositely charged electrodes (collectors) and accumulate on them.

Air purifiers with this type of filter usually retain slightly less pollution than HEPA, but are able to filter more air in a given time unit. Generally speaking, they are also quieter and more energy-efficient. The problem that some people pay attention to in the case of electrostatic precipitators is the potential production of small amounts of ozone, which can have negative effects, e.g. for asthmatics.

Carbon filters

No matter which type of purifier you choose, none of the above-mentioned filters can cope with unwanted odors, cigarette smoke or volatile organic compounds (VOC) such as benzene. Carbon filtersare the ones used for this. Therefore, if we expect comprehensive air purification, we cannot skip them. The activated carbon contained in them, in addition to physically retaining some impurities that have passed through the HEPA or electrostatic filter, absorbs some chemical compounds.

carbon filter

Manufacturers often ensure that air purifiers with individual filters also remove bacteria and viruses. This is only partly true. Indeed, the size of bacteria usually prevents them from getting through HEPA filters and allows them to stick to electrostatic filters. However, some bacteria and absolutely all viruses are too small to be effectively filtered from the air. The additional function of UV lamp isn’t always effective in neutralizing bioaerosols as well. Some bacteria and viruses are resistant to this type of radiation, and a few seconds of exposure is usually too little to deal with them effectively. Certainly, some of the potential pathogens will be neutralized this way, but the effectiveness of purifiers with UV lamps is difficult to assess.

How to take care of air purifiers?

Every purifier, regardless of the type of filter, must be taken care of. However, depending on the number and type of filters, there will be different amount of work and financial effort.

Pre-filters, standard in most air purifiers, are reusable and all you need to do is wash them once every few months. The same is true for electrostatic precipitators – in an ideal scenario, one is enough for the entire lifetime of the equipment. Thanks to this, we don’t generate garbage and significantly reduce the costs. In turn, the cost of replacing a set of HEPA and carbon filters, depending on the purifier model, can be several hundred euro per month.

hepa filter

Carbon filters are usually replaced 3 times a year, HEPA once (with significant air pollution once every six months). These types of filters become clogged with time and are a more difficult obstacle to overcome by the flowing air. The performance of the filters decreases significantly over time, so it’s very important to replace (in the case of HEPA and carbon) or clean (in the case of preliminary and electrostatic) them regularly.

Markings and certificates

The purchase of an air purifier and regular replacement of its filters isn’t the end of expenses related to the use of such equipment. In order to really notice the effects of its operation, it must be turned on around the clock. Therefore, you have to reckon with slightly higher electricity bills. However, these amounts may be lower (and the environment less burdened) if you buy equipment with an Energy Star certificate. Air purifiers with this certificate can use up to 40% less energy. It is also worth paying attention to whether the model we selected has the Auto mode – thanks to it, it will adjust the filtration power to the degree of air pollution itself.

Jeśli kupujemy sprzęt w celu zniwelowania objawów alergicznych np. w okresie pylenia roślin, zaletą może być certyfikat ECARF (European Centre for Allergy Research Foundation). To oznaczenie znajduje się na urządzeniach przetestowanych pod kątem usuwania alergenów, które najwidoczniej spisały się w tym wyjątkowo dobrze. Podobne certyfikaty w Polsce wydaje PTA (Polskie Towarzystwo Alergologiczne).

If we buy equipment to reduce allergic symptoms, e.g. during plant pollination, the ECARF (European Center for Allergy Research Foundation) certificate may be an advantage. This certificate is found on devices tested for allergen removal that have apparently done extremely well.

AHAM (Association of Home Appliance Manufacturers) is an independent association from the USA testing air purifiers and determining their efficiency (CADR mentioned earlier). Their certificate also ensures that the size of the room that the equipment can handle is not overblown. Of course, we can also trust what the manufacturer wrote on the packaging, but in the case of less known brands (and not only them) it doesn’t always have to have reference to reality.


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