Special Issue "Research on Indoor Air Cleaners for Particulate, Microbiological, and Gaseous Pollutants (2nd Edition)"

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Air Pollution Control".

Deadline for manuscript submissions: 30 November 2023 | Viewed by 667

Special Issue Editor

Institut für Umwelt & Energie, Technik & Analytik e. V. (IUTA), 47229 Duisburg, Germany
Interests: aerosols; filtration; air cleaners; indoor air
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Special Issue Information

Dear Colleagues,

This Special Issue is a follow-up of the first Special Issue entitled “Research on Indoor Air Cleaners for Particulate, Microbiological and Gaseous Pollutants” (https://www.mdpi.com/journal/atmosphere/special_issues/Indoor_Air_Cleaners) published in Atmosphere in 2022.

With the growing awareness of air pollution, air cleaners have been used for decades to improve indoor air quality. This especially includes air cleaners for particulate pollutants, based either on established technologies such as fibrous (HEPA) filters and electrostatic precipitators or alternative filtration concepts. The relevant particle size range extends from ultrafine particles which are omnipresent in indoor environments up to coarse particles such as pollen or dust at workplaces. Throughout the COVID-19 pandemic, the global interest in indoor air cleaners has increased substantially as they can also contribute to minimizing infection risks by filtration or inactivation (e.g., by UV-C) of viruses or virus-carrying droplets. In addition to air cleaners for particulate pollutants, there are also solutions for gaseous pollutants, e.g., based on activated carbon or photocatalysis.

Although there has already been a lot of research on air cleaners, there are still many open questions: How can air cleaners be further optimized in terms of cleaning efficacy, power consumption, and noise emissions? How can long-term stability be determined and increased? How is the distribution of the cleaned air in a room affected by its geometry, furnishing, and occupancy? Can potential health benefits be tested with bioaerosols or demonstrated in toxicological or epidemiological studies? Scientific answers to these and further questions will at least deliver input for the current standardization project for indoor air cleaners of the International Electrotechnical Commission (IEC).

Contributions from all applicable fields are welcome, whether they deal with technical aspects of the devices and filters, new measurement techniques or methods for assessing the efficacy, observations or simulations in real environments, or studies on the health effects of indoor air cleaners.

Dr. Stefan Schumacher
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Atmosphere is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


  • indoor air cleaners
  • filtration
  • ultra-fine particles
  • bioaerosols
  • gaseous pollutants
  • COVID-19
  • test methods
  • simulations
  • field experiments
  • health effects

Published Papers (1 paper)

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Comparison of Portable and Large Mobile Air Cleaners for Use in Classrooms and the Effect of Increasing Filter Loading on Particle Number Concentration Reduction Efficiency
Atmosphere 2023, 14(9), 1437; https://doi.org/10.3390/atmos14091437 - 14 Sep 2023
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This study focuses on the effect of portable and large filter-based air cleaners (HEPA filters), which became popular indoors during the COVID-19 pandemic, and their suitability for classrooms (here 186 m3). The decay rates of the particle number concentration (PNC) were [...] Read more.
This study focuses on the effect of portable and large filter-based air cleaners (HEPA filters), which became popular indoors during the COVID-19 pandemic, and their suitability for classrooms (here 186 m3). The decay rates of the particle number concentration (PNC) were measured simultaneously at up to four positions in the room. It was found that the different air outlet configurations of the units have an effect on the actual PNC removal in the room when operated at the same volume flow rates. This effect of the airflow efficiency of the air cleaners (AP) in a classroom is quantified with an introduced Air Cleaning Efficiency Factor in this study to identify beneficial airflows. In this context, the effect of filter loading in long-term operation on the cleaning effect is also investigated. The emitted sound pressure levels of the APs are given special attention as this is a critical factor for use in schools, as well as power consumption. A total of six different devices were tested—two portable APs and four large APs. In order to achieve the necessary volume flow rates, three or four of the portable units were used simultaneously in one room, while only one of the large units was used per room. When used at the same air circulation rates in the room, the portable APs exhibit higher sound pressure levels compared to the large APs. At air circulation rates of 4–5 h−1, the portable APs exceeded a value of 45 dB(A). Two of the four large units reach sound pressure levels below 40 dB(A) at air circulation rates of 4–5 h−1, whereby both large units, which are positioned on the rear wall, realize a homogeneous dilution of the room air. This is achieved by an air outlet directed horizontally at a height above 2 m or diagonally towards the ceiling, which points into the room and partly to the sides. On the other hand, an air outlet directed exclusively to the sides or horizontally into the room at floor level to all sides achieves lower particle decay rates. To investigate the influence of the filter loading, three large APs were operated in a school for a period of one year (190 days with 8 h each). For the three APs, long-term operation leads to different changes in PNC reduction efficiency, ranging from −3% to −34%. It is found that not only the size of the prefilter and main filter has a significant influence, but also whether there is a prefilter bypass that negatively affects the loading level of the main filter. At the same time, it was shown that one type of AP, measuring the pressure drop across the filters and readjusting the fan, kept the circulation rate almost constant (up to −3%) over a year. Full article
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