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. 2021 Aug 25;18(17):8955. doi: 10.3390/ijerph18178955

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© 2021 by the authors.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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Number concentrations of sub-0.5-, 0.5-, 1-, and 2.5-μm particles measured in the generation zone for (a–d) closed-door cases with (a) air purifier off, (b) low-speed air purifier turned on after particle generation, (c) high-speed air purifier turned on after particle generation, (d) and high-speed air purifier running from the beginning of particle generation; and (e,f) open-door cases with (e) air purifier off and (f) high-speed air purifier running from the beginning of particle generation. The background concentration is shown with the red horizontal line for <0.5- and 0.5-μm particles, green dash line for 1-μm particles, and blue dotted line for 2.5-μm particles. The removal time for different particle sizes is marked with asterisks.

Number concentrations of sub-0.5-, 0.5-, 1-, and 2.5-μm particles measured in the generation zone for (a–d) closed-door cases with (a) air purifier off, (b) low-speed air purifier turned on after particle generation, (c) high-speed air purifier turned on after particle generation, (d) and high-speed air purifier running from the beginning of particle generation; and (e,f) open-door cases with (e) air purifier off and (f) high-speed air purifier running from the beginning of particle generation. The background concentration is shown with the red horizontal line for <0.5- and 0.5-μm particles, green dash line for 1-μm particles, and blue dotted line for 2.5-μm particles. The removal time for different particle sizes is marked with asterisks.