Effectiveness Of Air Cleaners Research Articles

Effects of a gas-phase air cleaner in removing human bioeffluents and improving perceived air quality

The use of air cleaners to enhance indoor air quality under reduced ventilation for energy conservation has increasingly garnered attention. However, the effects of air cleaners on the removal of gaseous compounds require further research. Reduced ventilation can increase air pollution caused by emissions from humans (bioeffluents); however, little is known about the performance of air cleaners regarding this type of pollution. Thus, this study addressed this gap. Two male participants sitting in a stainless-steel chamber served as a source of bioeffluents at two temperatures (23°C and 28°C), and a gas-phase air cleaner was either operational or idled. Thirteen participants evaluated the air quality, and chemical analyses were performed. The protocols partially followed the ISO Standards 16,000–28 and 16,000–44. The results indicate that pollutants emitted by humans decreased when the air cleaner was operating. In addition, sensory assessments showed a decrease in odour intensity and percentage of dissatisfaction with the operating air cleaner. The clean air delivery rate was higher at 28 °C, and the perceived air freshness also improved at this temperature. Our findings show that air cleaner operation effectively improved the quality of air polluted by human bioeffluents. However, the validation of results in actual environments is recommended.

Elevator Ventilation and SARS-CoV-2-Relevant Particulate Matter Removal in Three Older California Elevators

The objective of this study was to measure particulate matter (PM) total loss rates in three older (1940s, 1960s, and 1980s) elevators in California during two phases and three low-cost intervention modes. Tracer gas decay and <2 μm aerodynamic diameter nontoxic NaCl particles (PM2) were used to calculate PM2 loss rates. The NaCl particles were considered surrogates for smaller particles carrying SARS-CoV-2. Empirical PM2 loss rates were paired with modeled dynamic scenarios to estimate SARS-CoV-2-relevant PM2 removal. Mean loss rates (hr-1) ranged from 1.8 to 184. Compared to a closed-door, stationary elevator, the moving elevators had a fourfold increased mean loss rate (hr-1), while an air cleaner in a stationary elevator increased the mean loss rates sixfold. In a dynamic particle removal simulation of a ten-story elevator, PM was removed 1.38-fold faster with an air cleaner intervention during bottom and top floor stops only (express ride) and 1.12-fold faster with an air cleaner during every other floor stops. The increase in removal rates due to the air cleaner was modest due to the higher moving and open-door removal rates, except during stationary phase. The half-life of PM2 particles in a stationary elevator after all passengers have left can be 8-12 minutes following a single emission and 2-5 minutes with an air cleaner. The low particle removal rate in the stationary elevator requires an intervention so that the particle removal rate will be high to eliminate infectious aerosol. If codes permit, keeping the door open when the elevator is stationary is most effective; otherwise, an air cleaner in a stationary elevator should be used. While an air cleaner is commonly seen as a substantial improvement in reducing potential virus concentration in air, in the moving elevator scenarios, the effect is quite modest. This paper provides empirical particle loss rates inside elevators, the effectiveness of air cleaners in a dynamic elevator space, two approaches to control infectious agents while the elevator is stationary, and support for a precautionary approach towards elevator use amidst a pandemic.

Effectiveness of a portable personal air cleaner in reducing the airborne transmission of respiratory pathogens

The airborne transmission in indoor environments represents the main pathway of respiratory pathogens, and most of the indoor environments do not have adequate ventilation to contain the risk of infection. This is particularly relevant for gathering spaces such as restaurants, schools, offices, etc. due to the long exposure times and high crowding levels.In this paper we investigated the effectiveness of a novel patented personal air cleaner in reducing the airborne transmission of respiratory pathogens both in close proximity (considering a typical face-to-face configuration at a conversational distance) and in shared indoor environments despite maintaining distancing (lecture room). The effectiveness of the portable protection device was investigated using complex transient 3D Computational Fluid Dynamics (CFD) numerical simulations. The mathematical model employed, validated through experimental measurements, is based on a Eulerian-Lagrangian approach, describing the air flow as the continuous phase and infectious respiratory particles as the discrete phase.The CFD analyses revealed that the air cleaner could strongly reduce the inhalation of respiratory pathogens in both the investigated scenarios. The air cleaner effectiveness in the case of a close proximity scenario, expressed as relative reduction of volume of infectious respiratory particles inhaled by the exposed subject, resulted >92%. In the case of use in a shared indoor environment, instead, during a 2-h lesson, the relative reduction of volume concentration of infectious particles in the breathing zone of the exposed subject was >99%.

Studying the efficiency of air cleaners at removing various indoor air impurities in classrooms and the relation to pupils’ symptoms

The existing knowledge on the effect of air cleaners in reducing different indoor impurities and health symptoms in real-life applications is still insufficient. PUHHO study aimed to fill this knowledge gap with a blinded intervention study in 18 primary school classrooms. The study was conducted during 8 weeks with 2 weeks without air cleaner, 3 weeks with air cleaner in full operation (filtration) with moderate airflow (200 - 400 m3/h) and 3 weeks sham operation (air cleaner blowing air without filtration). The latter two interventions were conducted in a blinded and mixed setup. Small, but statistically non-significant reductions in particulate matter levels (PM2.5; particulate matter with diameter less than 2.5 µm and PM10; diameter of particles less than 10 µm) were observed when comparing air cleaner filtration to air recirculation alone (sham operation). The use of air cleaners had no significant effect on the level of total volatile organic compounds (TVOC). Air cleaners did not have significant effect on the microbial levels or on the microbiome of the classrooms. Filtration by air cleaners was found to statistically significantly reduce upper (4.0%) and lower airway (2.5%) and other (4.0%) symptoms, but a nearly equivalent effect was observed with air recirculation alone.

Effect of air cleaners on early and late asthmatic response in asthmatic subjects sensitized to cat in ALYATEC’s environmental exposure chamber (EEC)

Effect of air cleaners on early and late asthmatic response in asthmatic subjects sensitized to cat in ALYATEC’s environmental exposure chamber (EEC)

Real-time measurements of PM2.5 and ozone to assess the effectiveness of residential indoor air filtration in Shanghai homes.

Portable air cleaners are increasingly used in polluted areas in an attempt to reduce human exposure; however, there has been limited work characterizing their effectiveness at reducing exposure. With this in mind, we recruited forty-three children with asthma from suburban Shanghai and deployed air cleaners (with HEPA and activated carbon filters) in their bedrooms. During both 2-week filtration and non-filtration periods, low-cost PM2.5 and O3 air monitors were used to measure pollutants indoors, outdoors, and for personal exposure. Indoor PM2.5 concentrations were reduced substantially with the use of air cleaners, from 34±17 to 10±8µg/m3 , with roughly 80% of indoor PM2.5 estimated to come from outdoor sources. Personal exposure to PM2.5 was reduced from 40±17 to 25±14µg/m3 . The more modest reductions in personal exposure and high contribution of outdoor PM2.5 to indoor concentrations highlight the need to reduce outdoor PM2.5 and/or to clean indoor air in multiple locations. Indoor O3 concentrations were generally low (mean=8±4ppb), and no significant difference was seen by filtration status. The concentrations of pollutants and the air cleaner effectiveness were highly variable over time and across homes, highlighting the usefulness of real-time air monitors for understanding individual exposure reduction strategies.

Effects of air cleaners and school characteristics on classroom concentrations of particulate matter in 34 elementary schools in Korea

Exposure to particulate matter (PM) in school environments has been associated with respiratory illnesses among children. Although using air cleaners was reported to reduce PM exposure and improve residents' health in homes, their effects in classrooms are not well understood. We examined how the use of air cleaners in classrooms and school/classroom characteristics affect the levels of indoor PM. Our environmental study included 102 classrooms from 34 elementary schools located on the mainland peninsula and an island in Korea. Indoor and outdoor PM were monitored simultaneously with portable aerosol spectrometers, and indoor gravimetric PM levels were measured with low volume, size-selective samplers during the class hours. Correlations among PM measurements were computed and final multiple regression models for indoor PM were constructed with a model building procedure. Correlation between indoor and outdoor PM2.5 (PM < 2.5 μm in aerodynamic diameter) was higher (r = 0.78, p < 0.01) than that of PM10 (PM < 10 μm) (r = 0.49, p < 0.01). School location, classroom occupant density, and ambient PM levels significantly (p-values<0.05) affected classroom PM concentrations. The adjusted PM levels in classrooms using air cleaners were significantly (p-values<0.01) lower by approximately 35% than in classrooms not using them. However, air cleaners appeared to remove PM2.5 more effectively than PM10, perhaps because coarse particles settle more rapidly than fine particles on surfaces, or their resuspension and generation rate by occupants exceeds the removal rate by air cleaners. Our study suggests that routine cleaning to remove surface dust along with the use of air cleaners might be required to effectively reduce occupants’ exposure in classrooms.

Effect Of Air Cleaners (Intense Pure Air® XL) On Early And Late Asthmatic Response In Asthmatic Subjects Sensitized To Cat In ALYATEC's Environmental Exposure Chamber (EEC)

Effect Of Air Cleaners (Intense Pure Air® XL) On Early And Late Asthmatic Response In Asthmatic Subjects Sensitized To Cat In ALYATEC's Environmental Exposure Chamber (EEC)

Deposition Removal of Monodisperse and Polydisperse Submicron Particles by a Negative Air Ionizer

Indoor particulate matter exposure is one of the main environmental risk factors influencing human health. Previous studies have indicated that the degree of hazards about ultrafine particles was associated with the particle surface area and number concentration. Polydisperse submicron particles (PSPs) contribute most of the indoor aerosol particle number and are usually used for removal testing. However, the behaviors of monodisperse submicron particles (MSPs) are easier to analyze. This study aims to investigate the difference between the deposition removal efficiency of MSP and PSP by the negative air ionizer (NAI) under different settings of freestream air velocity (FAV). The particle-removal experiments were conducted in a stainless steel test chamber under the condition of 50% relative humidity and FAV of 0.56, 1.2 and 2.0 m/s. The NaCl and oleic acid PSPs were generated from a constant output atomizer and the NaCl MSPs (30, 50, 100, 170 and 300 nm) were generated by passing the polydisperse NaCl aerosol through a Differential Mobility Analyzer. The concentration and size distribution of the particles in the chamber were monitored with a Scanning Mobility Particle Sizer (SMPS). The decay constant of particles number concentration, particle removal efficiency (PRE), enhancement factor of deposition rate (EF) and air cleaner effectiveness (ACE) were determined from the SMPS data. The decay constant of particle number concentration increased with the decrease of FAV and decreased with the increase of particle size. Both of the PREs of MSP and PSP were quite high, especially for the smaller particles and under low FAV. The EFs ranged from 4.4 to 115.5 and were proportional to the particle size. In addition, the ACE ranged from 0.57 to 0.96 and increased as the particle size increased. These results give a better understanding of the deposition of 30– 300-nm particles enhanced by the NAI and the influential factors.

Effect of an Air Cleaner with Electrostatic Filter on the Removal of Airborne House Dust Mite Allergens

PurposeThe effects of air cleaners on the removal of airborne indoor allergens, especially house dust mites (HDM), are still controversial. The objective of this study is to evaluate the effect of an air cleaner with an electrostatic filter on the removal of airborne mite allergens.Materials and MethodsA dried HDM culture medium that contained mite body particles and excretions was dispersed in a chamber equipped with an electrostatic air cleaner. The number of airborne particles was recorded continuously by a dust spectrometer for 60 minutes. Airborne particles in the chamber were collected on a sampling filter at a flow rate of 10 L/min and the Der f 1 concentration in the filter extracts was measured by two-site ELISA.ResultsThe air cleaner efficiently removed airborne HDM particles. The air cleaner removed airborne HDM particles (size 2-12.5 µm) 11.4 ± 2.9 fold (cleaner operating for 15 minutes), 5.4 ± 0.7 fold (cleaner operating for 30 minutes), and 2.4 ± 0.2 fold (cleaner operating for 60 minutes) more than the removal of HDM particles by natural settle down. Removal kinetics differed according to the particle size of the airborne particles. The air cleaner decreased the concentration of Der f 1 in the extraction of airborne particles collected on the air sampling filter by 60.3%.ConclusionThe electrostatic air cleaner can remove airborne HDM allergens and may be useful as a supplementary environmental control tool for HDM sensitized respiratory allergic patients.

Infiltration of forest fire and residential wood smoke: an evaluation of air cleaner effectiveness

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.

Infiltration of Forest Fire and Wood Smoke: An Intervention Study to Assess Air Cleaner Effectiveness

P-289 Introduction: Forest fires and residential wood-burning are significant sources of air pollution. PM2.5 from these sources has been linked to adverse health effects. Consequently, exposed populations should be provided with evidence-based recommendations on exposure reduction. Recommendations typically include remaining indoors and use of air cleaners, yet little information is available on PM infiltration during smoke episodes or on effectiveness of air cleaners in reducing indoor concentrations. Specific research objectives of this study were to measure indoor infiltration of outdoor PM2.5 from forest fires/residential wood-smoke and to determine effectiveness of High Efficiency Particulate Air (HEPA) filter air cleaners in reducing indoor PM2.5. Methods: Indoor and outdoor PM2.5 sampling was conducted over a 48-hour period in 21 homes during winter and in 16 homes during summer. Winter sampling was conducted in 2004 in a northern Canadian community affected by residential wood-burning. Summer sampling was conducted in 2004 and 2005 in southern British Columbia, Canada in communities impacted by forest fire smoke. Continuous 1-minute averages using a light-scattering device (personal DataRAM) and integrated 48-hour filter samples (Harvard Impactor) of PM were collected for each home. A portable HEPA filter air cleaner was operated indoors during the entire sampling period, however the filter was removed for 1 of the 2 days. Infiltration factors (Finf) were calculated using a recursive model (Switzer and Ott. 2001) after removal of indoor-generated PM2.5 data using censoring algorithms (Allen et al. 2003). Results: Valid 48 hour samples were obtained from 19 homes in winter and 12 homes in summer. Average wintertime PM2.5 concentrations were 14.2ug/m3 and 35.6ug/m3 for indoor and outdoor measurements respectively. Average summer concentrations were 12.3ug/m3 and 29.2ug/m3 for indoor and outdoor measurements respectively. For days when the filter was not used, mean Finf± SD values of 0.29±0.20 and 0.53±0.32 were found for winter and summer homes respectively. On days with filter use, Finf± SD was lower in both seasons with values of 0.11±0.10 and 0.22±0.24 for winter and summer respectively. Mean± SD air cleaner efficiencies ([Finf without filter - Finf with filter]/ Finf without filter) in summer and winter were 74±40% and 49±41% respectively. Effects of housing characteristics on infiltration and air cleaner efficiency based on multivariate models will also be presented. Discussion and Conclusions: For exposures to wood and forest fire smoke, infiltration was higher in summer versus winter and in both seasons air cleaners were effective in lowering Finf.

Consultation and referral guidelines citing the evidence: How the allergist-immunologist can help

Consultation and referral guidelines citing the evidence: How the allergist-immunologist can help

Book Review: Clinical Effects of Air Cleaners in Homes of Asthmatic Children Sensitized to Pet Allergens

Book Review: Clinical Effects of Air Cleaners in Homes of Asthmatic Children Sensitized to Pet Allergens

Effect of Air Cleaners on Mold Count in the Air and on the Symptoms of Perennial Rhinitis

Seventy-five children (ages 4 to 14 years) with perennial rhinitis caused by mold allergy (36 had asthma) were enrolled in an air-cleaner study for 2 years. Symptom scores prior to the study were compared with scores 1 and 2 years after placement of air-cleaners in the bedrooms. Forty-two homes were surveyed for mold count in the air in summer and winter, and the results compared with symptom changes. Improvements were found in quality of sleep (96 vs. 99%), sneezing (80 vs. 90%), scratchy throat (75 vs. 80%), night cough (75 vs. 83%), better mood in the morning (65 vs. 80%), postnasal drip (70 vs. 77%), nasal congestion (70 vs. 72%), night wheezing (70 vs. 83%), and sinus infection (50 vs. 55%). Parents reported a decrease in the use of both over-the-counter (76 vs. 80%) and prescription (43 vs. 48%) drugs. When the weekly symptom score sheets were compared, symptom recurrence rates were found to be clustered in the winter. These symptoms were cough (35%), nasal congestion (35%), sinus infection (32%), and postnasal drip (20%). The average mold counts (expressed as colony-forming-units per cubic meter of air) in the filtered bedrooms, in the unfiltered bedrooms, and outdoors were 310, 425, and 927 in the summer, and 689,762, and 1213 in the winter, respectively. The higher mold count in the winter may explain the increase in symptoms during that season. We observed a significant improvement in respiratory symptoms for 2 years following the installation of air-cleaners in the bedrooms of 75 children with perennial rhinitis due to mold allergy.

Evaluation of the Effectiveness of Several Air Cleaners for Reducing the Hazard from Indoor Radon Progeny

In studies conducted in the early 1980s, it was suggested that the use of room-type air cleaners were relatively ineffective in reducing the hazards associated with the presence of radon decay products in indoor air. Some studies suggested that air cleaning could actually increase the dose delivered by the decay products by shifting the activity-weighted particle size distribution to smaller sizes to the point where dose increase even though exposure decreased. A recently developed automated, semicontinuous instrument now permits the direct measurement of activity-weighted size distributions in occupied homes so that the exposure to those occupants can be directly determined and the effect of the air cleaners on dose be estimated. Three different types of air cleaners were tested in this study; an electrostatic air cleaner (EAC), an ion generator / fan system (IG / F), and a filtration unit that was operated at two different fan speeds (LO-FIL and HI-FIL). The three units reduced the median exposure to ra...

The effects of air cleaners on hay fever symptoms in air-conditioned homes

High-efficiency air cleaners that remove 99% of particles greater than 6 μ from the air are now available. We performed an 8-wk prospective double-blind crossover study of the efficacy of the addition of these cleaners to home central air conditioning. Twenty adults, allergic to ragweed, Alternaria, or both, kept daily medication records and symptom scores. We recorded daily outdoor pollen and mold counts, bimonthly inside and outside the home pollen and mold counts, and a physician's evaluation of efficacy. When the cleaners were in place, there was a trend toward lower symptom scores and also daytime and evening scores. Only the decrease in symptoms which occurred during night hours when the cleaners were in place were statistically significant. The correct sequence of cleaner placement was identified in 14 of the 20 cases. We conclude that the addition of a high-efficiency central air cleaner may add minimal improvement in hay fever to that provided by central air conditioning alone. The practical value of the device remains to be determined.