Room Air Cleaners Research Articles

The effect of room air cleaners on infection control in day care centres

The aim of this study was to assess the effectiveness of air cleaning in reducing the risk of respiratory infection in two day care centres using a simple and robust calculation model. Additionally, we aimed to identify potential hotspots for infections in indoor setting and focus countermeasures accordingly. Initial results from an interventional clinical study are provided as proof-of-concept for the model. We constructed a mathematical model to assess the number of persons at risk for airborne infection transmission in day care. Utilizing the model, we used portable air cleaners in two day care units (A and B, number of children participating in the study n = 43) and compared infection incidents between the two intervention units to the rest of the units in city of Helsinki (n = 607). The intervention buildings had mechanical supply and exhaust air ventilation. The risk modelling suggests that the use of air cleaners reduced the expected number of persons at infection transmission risk significantly. At day care centre A the average reduction was 60% (range 52% - 88%) and at day care centre B 53% (range 14% - 59%). During the approximately six month study period, we observed a significant difference in the days absent from day care due to infections between the intervention and reference day care units. On average, the parents were absent from work due to child’s illness in reference day care centers for 5.53 days and 3.77 days in intervention day care centers during the study period (p=0.009). In relative terms the reduction was approximately 32%. Our study offers compelling evidence to support increasing non-infectious air flow rates in daycare centers during periods requiring infection risk management. This can be implemented with portable air cleaners as an effective and cost-efficient strategy for mitigating the spread of respiratory infections among children. The clinical results support the findings suggested by the theoretical model. Implications and impacts–Air cleaning seems to be an effective way to reduce infection risk in day cares–Identification of infection risk hotspot will help in desgining the preventive methods–Portable air cleaners offer an affordable and versatile solution also in buildings where existing ventilation is insufficient for infection risk management”

Standard precautions should include 'safe ventilation' to minimise far-afield airborne transmission in health and social care settings.

Standard precautions should include 'safe ventilation' to minimise far-afield airborne transmission in health and social care settings.

Air Disinfection for Airborne Infection Control with a Focus on COVID-19: Why Germicidal UV is Essential†.

Aerosol transmission is now widely accepted as the principal way that COVID‐19 is spread, as has the importance of ventilation—natural and mechanical. But in other than healthcare facilities, mechanical ventilation is designed for comfort, not airborne infection control, and cannot achieve the 6 to 12 room air changes per hour recommended for airborne infection control. More efficient air filters have been recommended in ventilation ducts despite a lack of convincing evidence that SARS‐CoV‐2 virus spreads through ventilation systems. Most transmission appears to occur in rooms where both an infectious source COVID‐19 case and other susceptible occupants share the same air. Only two established room‐based technologies are available to supplement mechanical ventilation: portable room air cleaners and upper room germicidal UV air disinfection. Portable room air cleaners can be effective, but performance is limited by their clean air delivery rate relative to room volume. SARS‐CoV‐2 is highly susceptible to GUV, an 80‐year‐old technology that has been shown to safely, quietly, effectively and economically produce the equivalent of 10 to 20 or more air changes per hour under real life conditions. For these reasons, upper room GUV is the essential engineering intervention for reducing COVID‐19 spread.

Personal exposure monitoring of PM2.5 among US diplomats in Kathmandu during the COVID-19 lockdown, March to June 2020

The 2019 Novel Coronavirus SARS-CoV 2 (COVID-1911COVID-19: 2019 Novel Coronavirus SARS-CoV 2, PM2.5: particulate matter with diameter smaller than 2.5 mg; BAM: Beta attenuation monitor, RAC: room air cleaner.) pandemic has severely impacted global health, safety, economic development and diplomacy. The government of Nepal issued a lockdown order in the Kathmandu Valley for 80 days from 24 March to 11 June 2020. This paper reports associated changes in ambient PM2.5 measured at fixed-site monitors and changes in personal exposure to PM2.5 monitored by APT Minima by four American diplomats who completed monitoring before and during lockdown (24 h for each period per person, 192 person-hours in total). Time activities and use of home air pollution mitigation measures (use of room air cleaners (RACs), sealing of homes) were recorded by standardized diary. We compared PM2.5 exposure level by microenvironment (home (cooking), home (other activities), at work, commuting, other outdoor environment) in terms of averaged PM2.5 concentration and the contribution to cumulative personal exposure (the product of PM2.5 concentration and time spent in each microenvironment). Ambient PM2.5 measured at fixed-sites in the US Embassy and in Phora Durbar were 38.2% and 46.7% lower than during the corresponding period in 2017–2019. The mean concentration of PM2.5 to which US diplomats were exposed was very much lower than the concentrations of ambient levels measured at fixed site monitors in the city both before and during lockdown. Within-person comparisons suggest personal PM2.5 exposure was 50.0% to 76.7% lower during lockdown than before it. Time spent outdoors and cooking at home were large contributors to cumulative personal exposure. Low indoor levels of PM2.5 were achieved at work and home through use of RACs and measures to seal homes against the ingress of polluted air from outside. Our observations indicate the potential reduction in exposure to PM2.5 with large-scale changes to mainly fossil-fuel related emissions sources and through control of indoor environments and activity patterns.

Evaluation of clean air delivery rates and operating cost effectiveness for room air cleaner and ventilation system in a small lecture room

In general, room air cleaners are rated according to clean air delivery rate (CADR). However, ventilation systems have not yet been assessed using a metric similar to CADR. This study establishes a new mass balance equation that compares the CADRs of a ventilation system and a room air cleaner. Experiments and CFD simulations were conducted to evaluate and compare the CADRs of room air cleaners and ventilation system in the view of removing particles from indoor air. In addition, the operating cost effectiveness of ventilation system and room air cleaner was investigated. The results showed that the room air cleaners showed their performance independently, even when two or more room air cleaners were operated simultaneously. In the ventilation system, an air filter with MERV11 or higher rating was recommended to reduce the indoor particle concentration when 100% outdoor air was supplied. It was possible to select an air filter with MERV11or lower rating when the recirculation airflow rate was increasing up to 70%. The CADR of the room air cleaner was higher than that of the ventilation system regardless of the particle size and the filter performance when the airflow rate was same. The operating cost effectiveness (CADR/kW) of the room air cleaner was higher than that of the ventilation system at the same airflow rate. Therefore, the room air cleaner must be more cost-effective than the ventilation system for reducing particle concentration indoors.

Transmission and Institutional Infection Control of Tuberculosis.

Tuberculosis (TB) transmission control in institutions is evolving with increased awareness of the rapid impact of treatment on transmission, the importance of the unsuspected, untreated case of transmission, and the advent of rapid molecular diagnostics. With active case finding based on cough surveillance and rapid drug susceptibility testing, in theory, it is possible to be reasonably sure that no patient enters a facility with undiagnosed TB or drug resistance. Droplet nuclei transmission of TB is reviewed with an emphasis on risk factors relevant to control. Among environmental controls, natural ventilation and upper-room ultraviolet germicidal ultraviolet air disinfection are the most cost-effective choices, although high-volume mechanical ventilation can also be used. Room air cleaners are generally not recommended. Maintenance is required for all engineering solutions. Finally, personal protection with fit-tested respirators is used in many situations where administrative and engineering methods cannot assure protection.

Air filtration in buildings – a potential technique for protecting occupants against fine particles from outdoor sources

People spend almost 90% of their time indoors. Thus, the supply air filtration in buildings plays an important role in the occupant exposure to fine particles of outdoor origin. Besides supply air filtration, room air cleaner is a potential measure for reducing the health risks of urban air fine particles. The primary aim of the study was to investigate the role of air filtration when protecting occupants against fine particles from outdoor sources. Efforts were also put to improve the efficiency of supply air filtration, and to clarify the feasibility of room air cleaners. Long-term measurements were made in three locations in urban and suburban environments (school building, apartment in multistorey building, and single-family house). Sophisticated aerosol instruments together with an automatic sampling system were used to measure indoor and outdoor aerosol concentrations and size distributions (size range 0.01 – 10 mm). The results were used to determine the efficiency of air filters and indoor/outdoor (I/O) ratios for fine particles of outdoor origin. The efficiency of supply air filtration can be easily improved up to 90%, and the I/O ratio can be significantly reduced, when compared to existing practices. The uncontrolled leakage air flows in buildings, however, limit the feasibility of supply air filtration, i.e. the achieved I/O ratios (particle size 0.3 mm) were in the range of 0.2-0.3. By using room air cleaners in combination with effective supply air filtration, the I/O ratio could be further reduced, in favorable conditions even below 0.1. The concentration of indoor fine particles originating from outdoors can be effectively reduced by improving the level of supply air filtration. This requires, however, that the uncontrolled leakage air flows are negligible compared with the supply air flow. Room air cleaner, with adequate capacity and acceptable noise level, is another potential option for reducing the occupant exposure to fine particles.

Simultaneous removal of formaldehyde and benzene in indoor air with a combination of sorption- and decomposition-type air filters

Urgent measures for indoor air pollution caused by volatile organic compounds are required in urban areas of China. Considering indoor air concentration levels and hazardous properties, formaldehyde and benzene should be given priority for pollution control in China. The authors proposed the use of air-cleaning devices, including stand-alone room air cleaners and in-duct devices. This study aimed to find the best combination of sorption and decomposition filters for the simultaneous removal of formaldehyde and benzene, employing four types of air filter units: an activated charcoal filter (ACF), an ACF impregnated with a trapping agent for acidic gases (ACID), a MnO2 filter (MDF) for oxidative decomposition of formaldehyde at room temperature and a photocatalyst filter (PHOTO) coupled with a parallel beam ultraviolet (UV) irradiation device. The performance of the combined systems under air flow rates of 35–165 m3 h−1 was evaluated in a test chamber (2 m3) with a constant gas generation system. The experimental results and data analysis using a kinetic approach showed the combined system of ACF, PHOTO and MDF significantly reduced both concentrations of formaldehyde and benzene in air without any unpleasant odours caused by the UV-induced photocatalytic reaction. The system was then evaluated in a full-size laboratory (22 m3). This test proved the practical performance of the system even at full scale, and also suggested that the filters should be arranged in the order of PHOTO/ACF/MDF from upstream to downstream. The proposed system has the potential of being used for improving indoor air quality of houses and buildings in China.

Detection of antibiotic resistance genes associated with methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci in hospital air filter dust by PCR

Dust from the pre-filters of stand-alone hospital isolation room air cleaners was tested by PCR for the presence of antibiotic resistance genes associated with methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylo- cocci. Resistance genes for three classes of antibiotics (aac(6 0 )-aph(2 00 ), ermA, and mecA) were detected in multiple samples, indicating the presence of genetic material and likely cells of multidrug-resistant MRSA and other staphylococci in hospital air and that stand- alone air cleaners can reduce airborne levels of these contaminants. Screening for vanA was negative. Our results further suggest that dust may serve as an important reservoir of genetic elements that can confer drug resistance.

Effectiveness of Air Filters and Air Cleaners in Allergic Respiratory Diseases: A Review of the Recent Literature

Air filtration is frequently recommended as a component of environmental control measures for patients with allergic respiratory disease. Residential air filtration can be provided by whole house filtration via the home’s heating, ventilation, or air conditioning system, by portable room air cleaners, or a combination of the two. Appliances to filter the sleep breathing zone also have been developed. High-efficiency whole house filtration, high-efficiency particulate air sleep zone air filtration, and high-efficiency particulate air room air cleaners all appear to provide various degrees of benefit. Recent studies of various types of filtration, used alone or as part of more comprehensive environmental control measures, are reviewed.

Airborne Infection Isolation Rooms – A Review of Experimental Studies

Ventilation guidelines for airborne infection isolation rooms (AIIRs) are highly variable in different countries indicating lack of actual knowledge about the guidance needed. However, US guidelines for AIIRs are extensive and have been widely adopted outside the US. AIIR performance has also been evaluated in numerous studies. For a long time, the aim has mainly been to evaluate how well the existing AIIRs meet US guidelines. For historical reasons, mixing-type ventilation has been emphasised and attention has been paid to air exchange rates, although the use of auxiliary devices, such as portable room-air cleaners and ultraviolet germicidal irradiation systems, has also been examined. Recently, the scope of the investigations has been widened. The most crucial issue is to minimise the potential for disease transmission and prevent the escape of contaminated air from the AIIR. Airflow direction inside the AIIR is also important and AIIRs minimise air leakage to save energy. On the other hand, it has been observed that efficient containment can be achieved even by using simple and inexpensive construction by considering pressure differential and air flow patterns. Nevertheless, additional research is needed to assist hospitals with improving their preparedness to cope with the threat of pandemics by building and using effective AIIRs.

Efficient test method for evaluating gas removal performance of room air cleaners using FTIR measurement and CADR calculation

We have developed a new test method for differentiating the gas-removal performance of indoor air cleaners by using Fourier-transfer infrared measurements and a clean-air-delivery-rate (CADR) calculation method in a closed test chamber (4 m 3). Eighteen air cleaners were evaluated using both the new method and the current Korean and Japanese test methods, using ammonia, acetic acid, acetaldehyde, and toluene as test gases. The Association of Home Appliance Manufacturers’ statistical method for calculating regression line slopes of test chamber gas concentrations during air cleaner operation was used. The standard deviations of CADRs for ammonia, acetic acid, and toluene, gases that were easily removed by the air cleaners in the test chamber, were 3.2, 751.3, and 13.4 times higher, respectively, than the gas-removal efficiencies determined using the current arithmetic calculation method, which uses the ratio of concentrations after 0 and 30 min of air cleaner operation. The new test method clearly differentiated the gas-removal performances of various air cleaners, especially for gases that are quickly removed by indoor air cleaners. Also, the single-pass removal efficiency of the air cleaners was obtained with a simple calculation: CADR/flow rate/0.83.

Numerical analysis for evaluating the “Exposure Reduction Effectiveness” of room air cleaners

An “Exposure Reduction Effectiveness” index is proposed to quantify the performance of room air cleaners based on their capability of reducing occupants' exposure to pollutants of interest. The index has advantages over existing index such as CADR. It is applicable to both room average and local breathing zones, and can be used to compare air cleaning with the other two IAQ strategies: ventilation and source reduction. A computational fluid dynamics model is developed and used to assess the effectiveness of a room air cleaner for VOCs and particles of different sizes. The simulation results show: (1) species transport model and drift-flux Eulerian model can be used to predict concentration distributions of gaseous pollutants and particulate matters when there's an air cleaner operating and CFD simulation is an efficient tool to analyze personal ventilation; (2) the Exposure Reduction Effectiveness (ERE) index is effective for describing the removal effectiveness of room air cleaners in local zones as well as the room average.

家庭用空気清浄機のホルムアルデヒド除去性能の劣化性に関する研究

家庭用空気清浄機のホルムアルデヒド除去性能の劣化性に関する研究

Low-cost interventions improve indoor air quality and children's health

Intervention in the home environment to reduce asthma triggers theoretically improves health outcomes for asthmatic children. Practical benefit from application of these interventions has proven difficult. This single-blind study tested the effectiveness of simple low-cost home interventions in improving health scores of children with asthma. Families with at least one asthmatic child were recruited. Initial health examination, health, and home assessments were conducted and targeted interventions were implemented. Interventions included dehumidification, air filtration, furnace servicing, and high-efficiency furnace filters. When present, gross fungal contamination was remediated. Asthma education was provided along with education in healthy home practices. Follow-up assessments were conducted after 6 months. Health surveys were completed at enrollment and follow-up. This study enrolled 219 children with asthma. Home inspections and interventions were conducted in 181 homes and 83 families completed all phases. Reduction in asthma and allergy-related health scores was shown in follow-up health surveys. Health improvements were significant for cough when heating, ventilation, and air conditioning (HVAC) service and dehumidification were used. Breathing problems were significantly improved for dehumidification, HVAC service, and room air cleaners. Total dust allergen load was reduced for the dehumidification group (p < 0.05). Mold spore counts were reduced one order of magnitude in 25% of the homes. Indoor spore counts adjusted for outdoor spore levels were reduced overall (p < 0.01). Simple low-cost interventions directed to producing cleaner indoor air coupled with healthy home education improve the indoor air quality and health in asthmatic children.

Human K10 epithelial keratin is the most abundant protein in airborne dust of both occupied and unoccupied school rooms

Previously it was demonstrated that the levels of large particles (>2 micron) and associated bacterial cell envelope markers increase greatly on occupation in schools; it was hypothesized that the source of both was shed human skin. In the current work to test this hypothesis, room air cleaners were used to collect airborne dust (>50-100 mg) from occupied and unoccupied school rooms which was then subjected to proteomic analysis. Proteins were extracted from the dust and separated using two dimensional gel electrophoresis (2D GE). In situ digestion of protein spots with trypsin released peptides, which were subsequently analyzed by matrix assisted laser desorption/deionization, time-of-flight mass spectrometry (MALDI-TOF-MS) and tandem mass spectrometry (MALDI-TOF-MS-MS). In Coomassie blue stained gels, a single spot generally dominated the 2D gels; this protein was identified by tandem mass spectrometry as K10 epithelial keratin. The results experimentally confirm previous anecdotal reports that human skin is readily shed into air and suggest that increased levels of microbial markers and large particles observed in occupied rooms are also derived from skin.

The buzz on room air cleaners : How effective are they for management of allergies and asthma?

Asthma can be triggered by both indoor and outdoor air pollution. There isn't much we can do to avoid the outside air pollution, but what about improving the quality of the air inside our homes? It makes sense that if we could clean the allergens and irritants from the air we breathe indoors, our asthma would be better managed—especially given that Americans spend 90% of their time indoors. The problem is that the medical studies just don't back this up. Indoor air filters alone do not seem to have much of an impact on improving asthma control. But air filtration systems are often recommended as part of an overall strategy of environmental controls.

The buzz on room air cleaners*1How effective are they for management of allergies and asthma?

Abstract Asthma can be triggered by both indoor and outdoor air pollution. There isn't much we can do to avoid the outside air pollution, but what about improving the quality of the air inside our homes? It makes sense that if we could clean the allergens and irritants from the air we breathe indoors, our asthma would be better managed—especially given that Americans spend 90% of their time indoors. The problem is that the medical studies just don't back this up. Indoor air filters alone do not seem to have much of an impact on improving asthma control. But air filtration systems are often recommended as part of an overall strategy of environmental controls.

Positive Effects of a Fresh Air Filtration System on Hay Fever Symptoms

Background: Avoidance of allergen exposure is the basic preventive measure in reducing symptoms of immediate-type allergies. As room air cleaners were found to have no benefic effect on general health, their use has not been recommended. The purpose of this study was to evaluate the effect of a fresh air filtration system installed in the bedrooms of non-air-conditioned homes on hay fever symptoms. Methods: In a placebo-controlled, double-blind, two-period, crossover study, we investigated the effectiveness of a fresh air filtration system installed in the bedrooms of volunteers suffering from hay fever. Results: Volunteers only suffering from pollinosis reported an improvement of their allergy symptoms. We observed a significant decrease in nighttime hay fever symptoms and an increase in morning peak expiratory flow rates (PEFR). No effects were recognized in volunteers who additionally had perennial allergy. Conclusion: Based upon these results, the installation of fresh air filtration systems in bedrooms should be recommended for patients suffering from hay fever.

Do air cleaners make a difference in treating allergic disease in homes?

The purpose of this review is to objectively critique available data regarding the clinical benefits of room air cleaners and to provide physicians and patients with a reasonable recommendation of their utility in treatment of inhalant allergic disease. Data were obtained from published studies and reviews. The specific reviewed studies met the following criteria: 1) selection of patients with clinical allergic disease confirmed by detection of allergen-specific immunoglobulin E; 2) use of an effective air filter; 3) clinical and laboratory evaluation of results; and 4) measurement of the results of air filtration on environmental allergen or airborne particulate levels. The studies were conducted in a double-blind manner. Conclusions of two previous reviews are also incorporated in this paper. The results of the published studies and summary reviews show minimal, if any, effectiveness of room air cleaners in treatment of allergic respiratory disease. Room air cleaners should not be recommended for people with inhalant allergic disease.