Indoor Air Purification Solutions

Indoor air quality in buildings is often degraded and the use of air purifiers can help protect the health of occupants. Improving indoor air quality is a public health issue and it is everyone's responsibility to contribute to it in their homes but also in businesses where it is the responsibility of employers to ensure a healthy work environment.

Numerous air treatment solutions are nowadays proposed, but not all of them are efficient.

There are products sold at all prices, using many technologies and it is difficult for a neophyte to know if they are really effective to treat indoor air pollution and efficient to preserve his health.

In addition to ventilation, indoor air treatment is a solution to significantly reduce indoor air pollution levels. In certain situations, it is even the only solution to prevent pollution.

Under what circumstances should an air purifier be used?

Indoor air treatment devices can be used preventively to reduce the risk of indoor air pollution or curatively to treat identified and persistent pollution.

Using an air purifier is beneficial for people suffering from asthma, allergies, lung disease, migraines or sleep disorders by reducing indoor air pollution levels.

Air purifiers can be installed in :

  •     Dwellings (living room, bedroom, children's room)
  •     Individual and collective offices and meeting rooms
  •     Office space in industrial buildings
  •     Workshops
  •     Warehouses
  •     Health professionals' offices (consultation room and waiting room)
  •     Professionals receiving the public such as notaries and lawyers
  •     Publicly Admitted Institutions (ERP) such as day care centers, nursery and elementary schools, colleges, high schools and universities.
  •     Nursery assistants
  •     Commercial premises receiving customers
  •     Sports halls


What are the most effective technologies for indoor air purification?

Several technological solutions are proposed to purify indoor air, however they are not all equal and some may even degrade indoor air quality. Choosing the right technology is therefore the most important criterion.

In 2017, French agency ANSES published a review of the main technologies used to purify indoor air such as filtration (HEPA and Activated Carbon), photocatalysis, ozone, plasma and ionization.

  • HEPA Filtration

Devices equipped with HEPA filters retain fine particles and the pollutants they contain such as heavy metals, pesticides, plasticizers and flame retardants. This technology is used by professionals (clean rooms, pharmaceutical industry) and particularly in medical environments.

  • Active Carbon Filtration

Air purifiers equipped with activated carbon filters retain gaseous pollutants such as VOCs. They are effective in eliminating odours. However, they are not very effective in reducing indoor air pollution by formaldehyde.

  • Photocatalysis

Under the action of UV radiation, nanoparticles of titanium dioxide transform water (ambient humidity) and oxygen in the air into highly reactive radicals, capable of cutting organic substances into ever smaller pieces to ultimately produce water and carbon dioxide (CO2). This technology is effective in reducing indoor air pollution by formaldehyde.

To date, only technologies based on filtration have proven their effectiveness.

Regarding the other technologies, ANSES recommends that additional investigations be carried out to demonstrate their performance and especially to prove the absence of risk of indoor air pollution during their operation. Indeed, during the tests, some technologies generated ozone (O3) which is a pollutant that is very irritating to the respiratory tract.

Technologies based on ozone, plasma and ionization are not recommended for indoor air treatment.

Finally, solutions based on the diffusion of essential oil(s) do not purify indoor air but on the contrary generate a very high level of VOC pollution.

VOCs and Odors
Pesticides, Plasticizers, Flame Retardants
Heavy Metals
HEPA (H13/H14)
Activated Carbon

Filtration (HEPA and Activated Carbon) and photocatalysis technologies can be combined.

The solutions proposed by YOOTEST are based on HEPA filtration, Active Carbon filtration and the destruction of pollutants by photocatalysis.

The efficiency of an air purifier is often presented with a CADR value (Clean Air Delivery Rate) determined for the treatment of cigarette smoke, dust and pollen. The higher the CADR value, the more effective the purifier is considered to be. The CADR value and the maximum size of the treated room can be checked with "AHAM Verifide". This certification was originally intended for the American market, which explains why not all purifiers on the European market are certified.

What are the criteria for choosing the right indoor air purifier?

The air treatment device must be selected according to the air volume of the room. It must be able to treat several times per hour the volume of the room.

Indeed, a purifier designed to treat a 30 m2 room will be ineffective to treat a 100 m2 room.

In the same way an apartment or offices divided into several rooms will require as many purifiers as separate rooms. For example, a purifier with a capacity of 100 m2 will not be able to treat the air in the bedrooms if it is located in the living room, but on the other hand, you will be able to move the device to the room you want to treat (usually when you are there).

It is recommended to have a volume of treated air equal to at least 10 times the surface of the room. The following table is given as an indication.


Surface (square meters)
Air flow rate (cubic meters/hour)

Performances often below the sales pitch

Some brands display very high levels of performance in their communications, based on the legitimate desire of everyone to breathe healthy air. However, these claims should be considered with caution. Indeed, the performances are often tested individually on the materials composing the device, in laboratory conditions that are sometimes not representative of the real conditions of use and rarely performed on marketed devices. Furthermore, long-term efficacy is rarely evaluated.

In reality, air purifiers are generally less efficient than the manufacturers' claims and regular maintenance is necessary to obtain an acceptable level of performance.

YOOTEST's scientific team, with over ten years of expertise in the field of laboratory IAQ analysis, has carried out research, analysis and comparison work to propose a selection of air purifiers whose technologies and performances allow an effective air treatment against the different types of indoor air pollution.

What is the interest of having an integrated sensor for measuring indoor air pollution?

Many models of indoor air purifiers integrate an electronic air pollution sensor. They are generally specific for fine particles or total VOCs.
They are useful for :

  •     Knowing the level of ambient pollution
  •     Measuring air purifier efficiency
  •     Indicate the need for maintenance
  •     Adjusting the treatment flow in automatic mode

These sensors give indicative and not very precise measurements but sufficient to adjust the flow of a machine. Moreover, they drift in time and require replacement after a few years of use at best.

What are the maintenance operations to be carried out to guarantee the efficiency of the indoor air treatment over time?

The HEPA and Active Carbon filters must be changed periodically. Indeed, they capture and store pollution and clog up as they are used. Their efficiency decreases over time and they consume more energy to operate.

For photocatalytic devices, it is necessary to change the UV lamp and photocatalytic media to maintain performance levels.

For obvious reasons, maintenance operations must be simple to perform. Maintenance on air purifiers should be scheduled once a year, even every 6 months when the pollution level is high.

In order to maintain adequate performance levels, the price of filters, UV lamp and photocatalytic support should be considered when choosing an air purifier.  It is therefore advisable to avoid buying equipment for which maintenance parts are not available or at too high a price.

Are air purifiers noisy?

As a rule, air purifiers suck in air with a motor. Depending on the model, the noise level produced can be high and not conducive to concentration and sleep.

To give you a scale of comparison here are some indicative values of noise levels:

  •     Normal conversation (at a distance of 1 m): 65 dB
  •     Standard vacuum cleaner: 70 dB
  •     Normal office environment: 50 to 60 dB
  •     Bedroom at night : 35 to 40 dB

Therefore, for use in a home or office it is recommended to choose a silent air purifier and to check the noise level during operation. This is normally indicated on the product data sheet. If the fan is dirty during use, this can lead to an increase in noise.