Evaluation of the decontamination efficacy of a portable air cleaner using 275-nm UVC-LED radiation against airborne Coronavirus and Influenza virus

Assessing the effectiveness of portable HEPA air cleaners for reducing particulate matter exposure in King County, Washington homeless shelters: Implications for community congregate settings

Effects of mechanical ventilation and portable air cleaner on aerosol removal from dental treatment rooms

Rationale: Indoor particulate matter is associated with worse chronic obstructive pulmonary disease (COPD) outcomes. It remains unknown whether reductions of indoor pollutants improve respiratory morbidity. Objectives: To determine whether placement of active portable high-efficiency particulate air cleaners can improve respiratory morbidity in former smokers. Methods: Eligible former smokers with moderate-to-severe COPD received active or sham portable high-efficiency particulate absolute air cleaners and were followed for 6 months in this blinded randomized controlled trial. The primary outcome was 6-month change in St. George's Respiratory Questionnaire (SGRQ). Secondary outcomes were exacerbation risk, respiratory symptoms, rescue medication use, and 6-minute-walk distance (6MWD). Intention-to-treat analysis included all subjects, and per-protocol analysis included adherent participants (greater than 80% use of air cleaner). Measurements and Main Results: A total of 116 participants were randomized, of which 84.5% completed the study. There was no statistically significant difference in total SGRQ score, but the active filter group had greater reduction in SGRQ symptom subscale (β, -7.7 [95% confidence interval (CI), -15.0 to -0.37]) and respiratory symptoms (Breathlessness, Cough, and Sputum Scale, β, -0.8 [95% CI, -1.5 to -0.1]); and lower rate of moderate exacerbations (incidence rate ratio, 0.32 [95% CI, 0.12-0.91]) and rescue medication use (incidence rate ratio, 0.54 [95% CI, 0.33-0.86]) compared with sham group (all P < 0.05). In per-protocol analysis, there was a statistically significant difference in primary outcome between the active filter versus sham group (SGRQ, β -4.76 [95% CI, -9.2 to -0.34]) and in moderate exacerbation risk, Breathlessness, Cough, and Sputum Scale, and 6MWD. Participants spending more time indoors were more likely to have treatment benefit. Conclusions: This is the first environmental intervention study conducted among former smokers with COPD showing potential health benefits of portable high-efficiency particulate absolute air cleaners, particularly among those with greater adherence and spending a greater time indoors.

Particle removal efficiency of a household portable air cleaner in real-world residences: A single-blind cross-over field study

SARS-CoV-2, the virus that causes COVID-19, can be spread by exposure to droplets and aerosols of respiratory fluids that are released by infected persons when they cough, sing, talk, or exhale. To reduce indoor transmission of SARS-CoV-2 between persons, CDC recommends measures including physical distancing, universal masking (the use of face masks in public places by everyone who is not fully vaccinated), and increased room ventilation (1). Ventilation systems can be supplemented with portable high efficiency particulate air (HEPA) cleaners* to reduce the number of infectious particles in the air and provide enhanced protection from transmission between persons (2); two recent reports found that HEPA air cleaners in classrooms could reduce overall aerosol particle concentrations by ≥80% within 30 minutes (3,4). To investigate the effectiveness of portable HEPA air cleaners and universal masking at reducing exposure to exhaled aerosol particles, the investigation team used respiratory simulators to mimic a person with COVID-19 and other, uninfected persons in a conference room. The addition of two HEPA air cleaners that met the Environmental Protection Agency (EPA)-recommended clean air delivery rate (CADR) (5) reduced overall exposure to simulated exhaled aerosol particles by up to 65% without universal masking. Without the HEPA air cleaners, universal masking reduced the combined mean aerosol concentration by 72%. The combination of the two HEPA air cleaners and universal masking reduced overall exposure by up to 90%. The HEPA air cleaners were most effective when they were close to the aerosol source. These findings suggest that portable HEPA air cleaners can reduce exposure to SARS-CoV-2 aerosols in indoor environments, with greater reductions in exposure occurring when used in combination with universal masking.

Introduction: Fine particulate matter air pollution (PM 2.5 ) exposure is associated with elevated circulating inflammatory biomarkers implicated in cardiovascular disease (CVD). Portable Air Cleaners (PAC)s reduce PM 2.5 exposure and may lower concentrations of inflammatory biomarkers. Methods: We performed a systematic review and meta-analysis of randomized crossover trials of in-home high efficiency particulate air (HEPA) PACs vs. sham control on changes in CRP, IL-6, and/or TNFα among adults with no smoking exposure using Medline, Embase, and Cochrane Central Register of Controlled Trials with the Ovid Platform, Inspec, Compendix, and Web of Science Core Collection. Two investigators (S.W, D.W.) independently screened and reviewed the studies. We used RevMan 5.3 to perform the meta-analysis. Results: Search results included 459 articles screened, 26 selected for full review, and 14 that met inclusion criteria, representing N=724 participants included in the meta-analysis. Ten studies reported CRP, 9 reported IL-6, and 5 reported TNFα. Based on WHO guidelines, 5 studies were in regions of extreme PM 2.5 exposure (&gt;35 μg/m 3 ), 3 were high (10-35 μg/m 3 ), 3 were low (&lt;10 μg/m 3 ), and 2 lacked baseline PM 2.5 . Median (± S.D.) duration of HEPA/sham use was 9 ± 6.6 days. Reductions in PM 2.5 ranged from 2.6 to 54.9 μg/m 3 (35-82%) and varied by baseline PM 2.5 , although reporting of baseline PM 2.5 was incomplete across trials. Compared to sham PAC use, active PACs were associated with a 7% lower CRP (95% CI -13%, 0%) and 12% lower IL-6 (-22%, -2%), P&lt;0.05 for both (Figure). Subgroup analyses demonstrated consistency of effect of PACs across levels of baseline PM 2.5 . Conclusions: Our data demonstrate that PAC use is associated with significant reductions in circulating CRP and IL-6, with a magnitude of effect similar to clinical trials of statins and IL-1β inhibition. Given the role of inflammation in CVD, PACs may be useful to reduce systemic inflammation and cardiovascular risk.

Outdoor traffic-related airborne particles can infiltrate a building and adversely affect the indoor air quality. Limited information is available on the effectiveness of high efficiency particulate air (HEPA) filtration of traffic-related particles. Here, we investigated the effectiveness of portable HEPA air cleaners in reducing indoor concentrations of traffic-related and other aerosols, including black carbon (BC), PM2.5 , ultraviolet absorbing particulate matter (UVPM) (a marker of tobacco smoke), and fungal spores. This intervention study consisted of a placebo-controlled cross-over design, in which a HEPA cleaner and a placebo "dummy" were placed in homes for 4-weeks each, with 48-hour air sampling conducted prior to and during the end of each treatment period. The concentrations measured for BC, PM2.5 , UVPM, and fungal spores were significantly reduced following HEPA filtration, but not following the dummy period. The indoor fraction of BC/PM2.5 was significantly reduced due to the HEPA cleaner, indicating that black carbon was particularly impacted by HEPA filtration. This study demonstrates that HEPA air purification can result in a significant reduction of traffic-related and other aerosols in diverse residential settings.

Portable air cleaners (PACs) equipped with high-efficiency particulate air (HEPA) filters are recommended to reduce indoor particulate matter (PM) exposure from wildfire smoke, particularly in regions like the Pacific Northwest, where seasonal wildfires affect air quality. While many studies have evaluated the long-term effectiveness of HEPA PACs, few have focused on the effects of dust loading and their performance in filtering woodsmoke over extended periods. This study investigated the impact of filter dust loading on the performance of a HEPA PAC (Winix C535, Winix America) in reducing woodsmoke particles. Filters were pre-loaded with varying amounts of ASHRAE ISO 12103–1 A2 fine test dust, and an exposure chamber was used to assess clean air delivery rate (CADR), airflow rate, and power consumption. Results indicated a significant decline in PAC performance with increasing filter loading, highlighting the importance of regular filter replacements to maintain effective operation. Based on simulations considering dynamic indoor PM2.5 concentration, in a typical scenario with a 90-m² room, baseline PM2.5 emission rates, and continuous operation at fan speed Level 2 (5-year mean indoor PM2.5: 2.99 μg/m3), it would take over 5 years for the PAC filters to accumulate 46 g of dust – an amount associated with a significant drop in CADR observed in the study. These findings suggest that the commonly recommended 1-year replacement schedule by manufacturers may be overly conservative for such conditions. By utilizing indoor air quality sensors to monitor PM concentrations, users can tailor filter replacement schedules to maintain optimal PAC performance in real-world environments.

P-317 Introduction: In this paper, we report the efficacy of a variety of in-duct and portable air cleaners for control of PM exposure indoors based on trials conducted under controlled conditions in a fully characterized test home. Methods: Aerosol challenge trials were test conducted inside a 120 m2 test home equipped with a typical forced air ventilation system. In-duct air cleaners included a conventional filter (F1), a pleated fabric filter (F5), a conventional electronic air cleaner (EAC), and a new electrostatics technology (ifD) that relies upon an annular field charger and collection flutes coated with a dielectric material. Portable air cleaners (PAC) included a 6.2 m3/min (220 cfm) unit with a HEPA filter and an ionic unit that operates without a fan (IB). Continuous size-resolved particle number concentrations from multiple rooms in the test home were used to ascertain particle decay rates, whole house particle concentrations, and steady-state particle concentrations following emission of a standard polydisperse fine test dust. Results: Particle decay rates and concentrations in the test home varied substantially among the in-duct and portable air cleaners evaluated. Decay rates for 0.3 to 0.5 μ m particles ranged from less than 0.1 per hour (h-1) when neither the air handling unit (AHU) nor an air cleaner (AC) were operated to 7.2 h-1 during operation of the ifD. Performance of five PAC (3.9 h-1) approached the EAC (4.6 h-1), while tests with one PAC and three IB both resulted in removal rates of approximately 1.4 and 0 h-1, respectively. Similar results were obtained for larger particle sizes including those that contribute most to PM2.5 mass concentrations, except that removal rates were greater overall because of particle deposition to surfaces within the home (Table 1).Table 1: Whole House Removal Rates for 1- 3 μm Particles Measured in a Central Room of the Test HomeSteady-state concentrations achieved by the various systems tested were inversely related to decay rate. For example, steady-state indoor levels for the ifD were 2% of outdoor concentrations, 4% for the EAC, 19% for the 1″ filter, 10% for 1 PAC, and 28% for three IB. Discussion and Conclusions: These experiments carried out under simulated real-world conditions indicate that particle removal rates and whole house particle number concentrations indoors can vary by a factor of 10 or more depending upon the use of in-duct and portable air cleaning systems in a home. These results indicate that the greatest reduction in exposure is achieved by high efficiency, high airflow in-duct air cleaning systems. Use of indoor air cleaners could be an important modifier of PM-health relationships observed in epidemiological studies.

Portable air cleaner use and biomarkers of inflammation: A systematic review and meta-analysis

Ultrafine particle (UFP) exposures have been associated with human morbidity and mortality. The removal of UFP from indoor air using portable air cleaners (PACs) of various technologies has not been studied in detail. In this study, 12 devices representing different PAC technologies were tested with an UFP challenge in a full-scale stainless-steel chamber. UFP generation and measurements were conducted using a six-jet atomizer and scanning mobility particle sizer, (SMPS) respectively. It was found that high-efficiency particulate air (HEPA) and electrostatic precipitator (ESP) PACs have the best performance in terms of UFP removal rate, with an electret-based PAC also showing comparably high removal rates. Using modeling based on the experimental findings, some PAC technologies were shown to be effective in reducing indoor UFP concentrations in a typical Quebec City residential room by a factor of about 90%. Negative and bi-polar ion generators were found to have mediocre UFP removal performance, while photocatalytic oxidation-, ozone generation- and ultraviolet germicidal irradiation (UVGI)-based PACs had very limited or no UFP removal capabilities. Estimates of costs per performance index (Capital + Operating Costs/Calculated Clean Air Delivery RateCADR) showed that the HEPA-1, ESP- and electrets (FEF)based PACs provided the highest value for money in terms of total UFP removal performance.

Portable air cleaners (PACs) equipped with HEPA filters are gaining attention as cost-effective means of decreasing indoor particulate matter (PM) air pollutants and airborne viruses. However, the performance of PACs in naturalistic settings and spaces beyond the room containing the PAC is not well characterized. We conducted a single-blinded randomized cross-over interventional study between November 2020 and May 2021 in the homes of adults who tested positive for COVID-19. The intervention was air filtration with PAC operated with the HEPA filter set installed (“filter” condition) versus removed (“sham” condition, i.e., control). Sampling was performed in 29 homes for two consecutive 24-hour periods in the primary room (containing the PAC) and a secondary room. PAC effectiveness, calculated as reductions in overall mean PM2.5 and PM10 concentrations during the filter condition, were for the primary rooms 78.8% and 63.9% (n = 23), respectively, and for the secondary rooms 57.9% and 60.4% (n = 22), respectively. When a central air handler (CAH) was reported to be in use, filter-associated reductions of PM were statistically significant during the day (06:00–22:00) and night (22:01–05:59) in the primary rooms but only during the day in the secondary rooms. Our study adds to the literature evaluating the real-world effects of PACs on a secondary room and considering the impact of central air systems on PAC performance.

Portable air cleaners with HEPA filtration and UV-C irradiation to reduce air contamination in a multi-patient dental environment.

Communities impacted by fine-particle air pollution (particles with an aerodynamic diameter less than 2.5 microm; PM(2.5)) from forest fires and residential wood burning require effective, evidence-based exposure-reduction strategies. Public health recommendations during smoke episodes typically include advising community members to remain indoors and the use of air cleaners, yet little information is available on the effectiveness of these measures. Our study attempted to address the following objectives: to measure indoor infiltration factor (F(inf)) of PM(2.5) from forest fires/wood smoke, to determine the effectiveness of high-efficiency particulate air (HEPA) filter air cleaners in reducing indoor PM(2.5), and to analyze the home determinants of F(inf) and air cleaner effectiveness (ACE). We collected indoor/outdoor 1-min PM(2.5) averages and 48-h outdoor PM(2.5) filter samples for 21 winter and 17 summer homes impacted by wood burning and forest fire smoke, respectively, during 2004-2005. A portable HEPA filter air cleaner was operated indoors with the filter removed for one of two sampling days. Particle F(inf) and ACE were calculated for each home using a recursive model. We found mean F(inf)+/-SD was 0.27+/-0.18 and 0.61+/-0.27 in winter (n=19) and summer (n=13), respectively, for days when HEPA filters were not used. Lower F(inf)+/-SD values of 0.10+/-0.08 and 0.19+/-0.20 were found on corresponding days when HEPA filters were in place. Mean+/-SD ACE ([F(inf) without filter-F(inf) with filter]/F(inf) without filter) in winter and summer were 55+/-38% and 65+/-35%, respectively. Number of windows and season predicted F(inf) (P<0.001). No significant predictors of ACE were identified. Our findings show that remaining indoors combined with use of air cleaner can effectively reduce PM(2.5) exposure during forest fires and residential wood burning.

Respiratory infections, including SARS-CoV-2, are spread via inhalation or ingestion of airborne pathogens. Airborne transmission is difficult to control, particularly indoors. Manufacturers of high efficiency particulate air (HEPA) filters claim they remove almost all small particles including airborne bacteria and viruses. This study investigates whether modern portable, commercially available air filters reduce the incidence of respiratory infections and/or remove bacteria and viruses from indoor air. We systematically searched Medline, Embase and Cochrane for studies published between January 2000 and September 2020. Studies were eligible for inclusion if they included a portable, commercially available air filter in any indoor setting including care homes, schools or healthcare settings, investigating either associations with incidence of respiratory infections or removal and/or capture of aerosolised bacteria and viruses from the air within the filters. Dual data screening and extraction with narrative synthesis. No studies were found investigating the effects of air filters on the incidence of respiratory infections. Two studies investigated bacterial capture within filters and bacterial load in indoor air. One reported higher numbers of viable bacteria in the HEPA filter than in floor dust samples. The other reported HEPA filtration combined with ultraviolet light reduced bacterial load in the air by 41% (sampling time not reported). Neither paper investigated effects on viruses. There is an important absence of evidence regarding the effectiveness of a potentially cost-efficient intervention for indoor transmission of respiratory infections, including SARS-CoV-2. Two studies provide 'proof of principle' that air filters can capture airborne bacteria in an indoor setting. Randomised controlled trials are urgently needed to investigate effects of portable HEPA filters on incidence of respiratory infections.