Testing Filter-Based Air Cleaners with Surrogate Particles for Viruses and Exhaled Droplets

Schumacher, Stefan; Sanchez, Arantxa Banda; Caspari, Anna; Staack, Katharina; Asbach, Christof

doi:10.3390/atmos13101538

Cited by 13 publications

(8 citation statements)

References 63 publications

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“…Fresh smoke particles can carry charge 34 and when deposited onto the filter build up a charge on the surface that serves to repel charged smoke aerosol. This loss of effectiveness has been observed with electrostatic filters loaded with cigarette smoke 35 and the effectiveness by discharging the filter using isopropyl alcohol. 36 The loss of effectiveness through charge buildup also explains why the flow was not greatly reduced but the filter was still ineffective at reducing PM 2.5 concentrations in the chamber.…”

Section: Filter Conditionmentioning

confidence: 92%

Impact of do‐it‐yourself air cleaner design on the reduction of simulated wildfire smoke in a controlled chamber environment

2022

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During wildfire smoke events public health agencies release advisories to stay indoors, close doors and windows, and operate a portable air cleaner (PAC). The do-ityourself (DIY) air cleaner consisting of a box fan and a furnace filter is a widely used low-cost alternative to commercial PACs because of its increased accessibility. In this study, we evaluate the clean air delivery rate (CADR) of different DIY air cleaner designs for reducing simulated wildfire smoke and identify operating parameters that may impact their performance and use. The simplest formulation of a DIY air cleaner (box fan with taped on minimum effectiveness reporting value -[MERV] 13 furnace filter) had a CADR of 111.2 ± 1.3 ft 3 /min (CFM). Increasing the fan flow by changing the fan type, increasing the fan setting, or reducing the pressure drop across the filtering surface increased the CADR. Large increases in CADR could be obtained by using a shroud (40%), using a 4″ thick filter (123%) using two filters in a wedge shape (137%), or using four filters in a Corsi-Rosenthal (CR) box design (261%). The CADR was greatly reduced with filters heavily loaded with smoke, pointing to the need for frequent filter changes during smoke events.

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Section: Filter Conditionmentioning

confidence: 92%

Impact of do‐it‐yourself air cleaner design on the reduction of simulated wildfire smoke in a controlled chamber environment

2022

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“…This work goes some way to addressing the need for robust research on the effectiveness of PAC devices in hospital settings (2,26,27), and its implementation would help reduce the crippling patient backlogs without exposing people to increased infection risk and without resulting in significant infrastructure costs. The use of PAC could also be beneficial in other indoor settings besides hospitals where the installation of built-in mechanical ventilation may be cost/time/energy prohibitive, such as offices, schools, universities etc, as indicated in previous research (28,29). Finally, the current study provides a simple and easily deployable method to assess and improve aerosol concentration.…”

Section: Discussionmentioning

confidence: 92%

Use of portable air purifiers to reduce aerosols in hospital settings and cut down the clinical backlog

et al. 2023

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SARS-CoV-2 has severely affected capacity in the NHS, and waiting lists are markedly increasing due to downtime of up to 50 minutes between patient consultations/procedures, to reduce the risk of infection. Ventilation accelerates this air cleaning, but retroactively installing built-in mechanical ventilation is often cost-prohibitive. We investigated the effect of using portable air cleaners (PAC), a low-energy and low-cost alternative, to reduce the concentration of aerosols in typical patient consultation/procedure environments. The experimental setup consisted of an aerosol generator, which mimicked the subject affected by SARS-CoV-19, and an aerosol detector, representing a subject who could potentially contract SARS-CoV-19. Experiments of aerosol dispersion and clearing were undertaken in situ in a variety of rooms with 2 different types of PAC in various combinations and positions. Correct use of PAC can reduce the clearance half-life of aerosols by 82% compared to the same indoor-environment without any ventilation, and at a broadly equivalent rate to built-in mechanical ventilation. In addition, the highest level of aerosol concentration measured when using PAC remains at least 46% lower than that when no mitigation is used, even if the PAC's operation is impeded due to placement under a table. The use of PAC leads to significant reductions in the level of aerosol concentration, associated with transmission of droplet-based airborne diseases. This could enable NHS departments to reduce the downtime between consultations/procedures Initialisms AGPAerosol Generating Procedure APS Aerodynamic Particle Sizer ENT Ear Nose Throat

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“…These mobile devices have a fan that draws in the room air, passes it through one or more filters, and releases the cleaned air back into the room [17]. Air cleaners have become increasingly popular in recent years, as they are known to reduce the concentration of infectious aerosols [18][19][20][21]. However, many air cleaners are also equipped with activated carbon (AC) filters to reduce the concentration of gaseous pollutants [22][23][24].…”

Section: Introductionmentioning

confidence: 99%

The Drawback of Optimizing Air Cleaner Filters for the Adsorption of Formaldehyde

Schumacher,

Caspari,

Schneiderwind

et al. 2024

Atmosphere

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Air cleaners with activated carbon (AC) filters for the adsorption of gaseous pollutants are often used to improve indoor air quality. As formaldehyde is a common and health-relevant indoor air pollutant, many testing standards for air cleaners, such as GB/T 18801:2015, require the cleaning efficacy to be tested with this substance. This often persuades manufacturers to optimize the employed filters specifically for formaldehyde. However, in regions where indoor formaldehyde levels are far below the guideline values, other gaseous pollutants might be more relevant. Thus, the question arises of whether the optimization for formaldehyde can have a negative impact on the adsorption of other gases. To address this question, the clean air delivery rate (CADR) of an air cleaner was determined for different test gases with either a standard AC filter or an AC filter modified for improved formaldehyde adsorption. Although the modified AC filter performed substantially better for formaldehyde, a strong reduction in the CADR was observed for toluene and nitrogen dioxide. This is a drawback for situations in which these gases are more problematic than formaldehyde. The findings suggest using either specialized filters for different applications or blends of different adsorbants to find the best compromise for the most relevant pollutants.

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Testing Filter-Based Air Cleaners with Surrogate Particles for Viruses and Exhaled Droplets

Cited by 13 publications

References 63 publications

Impact of do‐it‐yourself air cleaner design on the reduction of simulated wildfire smoke in a controlled chamber environment

Impact of do‐it‐yourself air cleaner design on the reduction of simulated wildfire smoke in a controlled chamber environment

Use of portable air purifiers to reduce aerosols in hospital settings and cut down the clinical backlog

The Drawback of Optimizing Air Cleaner Filters for the Adsorption of Formaldehyde

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