The safest technologies to clean indoor air and avoid health risks

by time news

Until the arrival of the covid-19 pandemic, indoor air was believed to be healthier than outdoor air due to the false belief that buildings give us shelter and therefore protect us. However, the reality is that indoor air can be up to five times more polluted than outdoor air.

Elena Jimenez Martinez

  • Professor of Physical Chemistry, University of Castilla-La Mancha

The worrying thing is that Between 80-90% of our time is spent indoors (offices, classrooms, shopping malls, homes, etc.). Therefore, most of the activities of a person’s daily life take place in closed spaces. Due to energy savings, these are usually ventilated very little in autumn and winter, which is exactly when there is a higher incidence of respiratory diseases.

The Conversation

Pathogen-laden aerosols

There are many diseases that are transmitted by the bioaerosols that we exhale. For example, the Covid-19 that caught the entire world off guard and took a heavy toll in lives: almost 2 million deaths in Europe, if we take into account the figures as of June 12, 2022).

The various pathogens that cause the most common upper respiratory tract infection among humans, the common cold, are also transmitted by air. without forgetting the flu, which causes approximately 70,000 deaths in Europe every year.

The best way to reduce the risk of contagion of these diseases while living indoors is good ventilation. Fundamentally because it brings in outside air, dilutes the pollutants present inside and regulates humidity and temperature.


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But what happens if it is not possible to ventilate constantly? What devices are on the market to clean the air of pathogens?

renew the stale air

The current regulations in Spain seek to achieve greater energy efficiency by promoting the construction of increasingly watertight buildings to isolate ourselves from the outside, and which also have controlled mechanical ventilation (CVM) to guarantee air renewal and maximum comfort. In fact, since 2020 the VMC is mandatory in newly built buildings in Spain. This type of ventilation consists of extracting the stale air from the interior with a fan and replacing it with previously filtered outside air.

Flu, Cold, Constipated, Constipate, Woman Coughing, Coughing, Coughing
Flu, Cold, Constipated, Constipate, Woman Coughing, Coughing, Coughing
EUROPA PRESS – Archive

However, in existing buildings without VMC it is important to implement solutions to clean and reduce the amount or activity of airborne pathogens. For this reason, the use of different technologies for cleaning the air in indoor spaces has increased. These include filtration, adsorption, ultraviolet light (UV) lamps, bipolar ionization, and photocatalysis.

Technologies to clean indoor air

1) the filtration, For example, with HEPA filters (high-efficiency particle filters), it consists of passing the indoor air through a filtering surface made of very fine fibers. Generally, randomly placed quartz fibers are used. This creates a mesh-like framework capable of retaining up to 99.97% of the aerosols with a diameter of 0.3 μm (one millionth of a meter) that pass through it.

2) adsorption It consists in the use of a material with a very porous structure (for example activated carbon or silica gel) with very high fixation and retention properties.

3) germicidal lamps they emit UVC radiation at 253.7 nm and inactivate the DNA of microorganisms.


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4) Photocatalysis uses photons of light and semiconductor materials, such as titanium dioxide (TiO₂), to generate reactive oxygen species that destroy pathogen membranes and, in the case of COVID-19, the protein envelope of the virus.

5) Regarding the ionizationions and free radicals are generated that also deactivate microorganisms.

Some technologies generate ozone and other harmful compounds

Filtration and adsorption do not generate any pollutants. However, the rest of the technologies initiate photochemical reactions that generate volatile organic compounds, ozone and small particles, which can cause harmful health effects ranging from respiratory problems to cardiovascular disorders and even cancer.

So, does this equipment not pass the pertinent tests that verify its safety? Do they not have the appropriate certifications when they are released to the market?

Yes, but sometimes the tests that are carried out are done in laboratory conditionsvery far from the actual conditions of use and the concentrations of the pollutants generated may be within the permissible values ​​by current regulations.

Thus, in a study of Georgia Institute of Technology (Atlanta, United States) The formation of ultrafine particles (less than 0.1 microns) has been observed during the operation of equipment based on photocatalysis. These very small particles can reach the pulmonary alveoli causing respiratory problems.


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In the University of Castilla-La Mancha (Spain) a study is being carried out to evaluate the formation of contaminants derived from the operation of an ionization-based device. Preliminary results indicate that high amounts of ozone are formed. In another study carried out at the University of Colorado (United States) the formation of ozone and particles was also detected during the use of UVC lamps.

Certainly, in the absence of VMC and where natural ventilation of an indoor space is not adequate or possible, air cleaners can be used. Of course, as long as they are based on technologies that do not generate pollutants that are harmful to our health.

This article has been published in The Conversation and Diana Rodríguez and María Antiñolo have also participated.

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