Indoor air quality: Technologies for pollutant removal and air purification

Indoor air quality has received increasing attention, particularly due to the recent emergence of several respiratory diseases1. Ventilation, natural and/or mechanical, is perhaps the most widely used strategy to decrease indoor air pollutant concentrations. However, if the outdoor air is more polluted, or in certain situations where ventilation is not possible, other strategies are necessary, such as source control and pollutant extraction.

Source control is the most intelligent strategy as it avoids the problem at its source. This is made possible through the selection of "cleaner" building materials and furniture that emit fewer pollutants. In this regard, the Indoor Air Quality service of INEGI has competences to support the industrial development of these materials and evaluate their impact on indoor environments. Through the Indoor Air Quality Laboratory, INEGI tests samples of various materials to determine the concentration of volatile organic compounds (VOCs) and low molecular weight aldehydes (formaldehyde, acetaldehyde, among others). It also collects air samples in service buildings and residences to characterize indoor air quality in these locations and support decision-making for improvement implementation.

Extraction incorporates air purification technologies, one of the emerging areas in this field. Various possible technologies include physicochemical technologies (e.g. filtration, adsorption, ultraviolet photocatalytic oxidation, disinfection, and ultraviolet ionization) and/or biological-based technologies (such as air purification methods with plants and methods based on microalgae). Also in this regard, INEGI's Indoor Air Quality Laboratory participated in studies to test the effectiveness of UV photocatalytic oxidation2 and can be a potential partner in studying the effectiveness of pollutant removal by different types of technologies.

Each technology has advantages and limitations. For example, some work well for a family of pollutants with similar characteristics, and are not applicable to all types of pollutants. Filtration applies more to particulate matter, while adsorption applies to certain chemical compounds. That is, no individual technology can remove all types of indoor air pollutants. The development of filters with other properties, such as chemisorption, through the development of nanofibers, may be another path to follow. However, adsorption technology also has disadvantages, such as the development of bacteria on the adsorbent surface, as well as producing a hazardous solid residue that must be treated and/or disposed of properly. Another field of research aims at incorporating adsorbents into building materials to remove airborne pollutants without requiring additional energy and with minimal formation of byproducts.

UV photocatalytic oxidation is a promising technology, as it covers organic and inorganic compounds, as well as microorganisms, but more studies are needed before it can be safely used in buildings. Its main disadvantage is incomplete oxidation, which produces reaction byproducts that may be more toxic or harmful to health than the original constituents (e.g. formaldehyde). This problem can also be observed in the use of ultraviolet light, which may lead to the release of ozone. In turn, the performance of biological systems (e.g. using plants and/or microorganisms) for removing indoor air pollutants depends heavily on the interactions between the pollutants, the plant, and the microorganisms in the growth medium. Thus, the main recommendations for biological systems include proper selection of species, growth medium, irrigation systems, lighting, and abiotic conditions (e.g. temperature and humidity). It is also important to consider the pollen load and allergenic potential of the plants3.

The use of combined technologies to broaden the spectrum of pollutants covered and, of course, the development of new materials using nanotechnology, seem to be two aspects to consider in research in this area4.

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Related Pages

Laboratory Services | Indoor Air Quality

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[1]T. M. Mata, F. Felgueiras, A.A. Martins, H. Monteiro, M.P. Ferraz, G.M. Oliveira,  M.F. Gabriel, G.V. Silva, "Indoor Air Quality in Elderly Centers: Pollutants Emission and Health Effects,” Environments, vol. 9, no. 86, pp. 1–26, 2022, doi: 10.3390/ environments9070086.

[2]R. A. R. Monteiro, A.M. Silva, J.R. Ângelo, G.V. Silva, A.M. Mendes, R.A. Boaventura, V.J. Vilar, "Photocatalytic oxidation of gaseous perchloroethylene over TiO2 based paint,” J. Photochem. Photobiol. A Chem., vol. 311, pp. 41–52, 2015, doi: 10.1016/j.jphotochem.2015.06.007.

[3]T. M. Mata, G. M. Oliveira, H. Monteiro, G. V. Silva, N. S. Caetano, and A. A. Martins, 

"Indoor air quality improvement using nature-based solutions: Design proposals to greener cities,” International Journal of Environmental Research and Public Health, vol. 18, no. 16. MDPI, Aug. 02, 2021, doi: 10.3390/ijerph18168472.

[4]T. M. Mata, A.A. Martins, C.S.C. Calheiros, F. Villanueva, N.P.A. Cuevilla, M.F. Gabriel, G.V. Silva, "Indoor Air Quality: A Review of Cleaning Technologies,” Environments, vol. 9, no. 118, pp. 1–29, 2022, doi: 10.3390/ environments9090118.