Soft Ionization: Improving Indoor Air Quality

In this paper we report two applications of a subcategory of air cleaning devices based on soft ionization that do not cause molecular fragmentation. A system that includes two unipolar ionizing modules has been used to simultaneously produce positive and negative ions in the air. In one set of experiments a large chamber (28 m3) was used to study the effect of ions on reducing PM1.0 particles produced by a research grade calibrated cigarette. The data presented in this paper were obtained using a carbon-brush-based bipolar ionizer and a MERV 10 filter with electret media in a recirculating HVAC system. Significant improvement in removal rate of fine and ultrafine particles was achieved when using the bipolar ionizer in conjunction with the MERV 10 filter. The second set of experiments were conducted using a 36 m3 chamber, following BSL-3 standards, to study the effect of ions on aerosolized SARS-CoV-2. Results of these investigations reveal the inactivation rate of SARS-CoV-2 are enhanced when ions are introduced in the air;inactivation rates were increased by more than 60%and 90%for ion densities of 10,000/cc and 18,000/cc. IEEE

Performance of in-duct bipolar ionization devices on pollutant removal and potential byproduct formation in indoor environments

The COVID-19 pandemic has highlighted the importance of indoor air quality (IAQ) since SARS-CoV-2 may be transmitted through virus-laden aerosols in poorly ventilated spaces. Multiple air cleaning technologies have been developed to mitigate airborne transmission risk and improve IAQ. In-duct bipolar ionization technology is an air cleaning technology that can generate ions for inactivating airborne pathogens and increasing particle deposition and removal while without significant byproducts generated. Many commercial in-duct ionization systems have been developed but their practical performance on pollutant removal and potential formation of byproducts have not been investigated comprehensively. The results in this study showed that the in-duct bipolar ionization technology can significantly improve the particle removal efficiency of the regular filter, while no significant ozone and ion were released to the indoor air. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Experimental study of the purification performance of a MopFan-based photocatalytic air cleaning system.

Severe acute respiratory syndrome coronavirus (SARS-CoV)-2, the virus that causes the coronavirus disease (COVID)-19, is primarily transmitted through respiratory droplets which linger in enclosed spaces, often exacerbated by HVAC systems. Although research to improve HVAC handling of SARS-CoV-2 is progressing, currently installed HVAC systems cause problems because they recirculate air and use ineffective filters against virus. This paper details the process of developing a novel method of eliminating air pollutants and suspended pathogens in enclosed spaces using Photocatalytic Oxidation (PCO) technology. It has been previously employed to remove organic contaminants and compounds from air streams using the irradiation of titanium dioxide (TiO2) surfaces with ultraviolet (UV) lights causing the disintegration of organic compounds by reactions with oxygen (O) and hydroxyl radicals (OH). The outcome was two functional prototypes that demonstrate the operation of PCO-based air purification principle. These prototypes comprise a novel TiO2 coated fibre mop system, which provide very large surface area for UV irradiation. Four commercially accessible materials were used for the construction of the mop: Tampico, Brass, Coco, and Natural synthetic. Two types of UV lights were used: 365 nm (UVA) and 270 nm (UVC). A series of tests were conducted that proved the prototype's functionality and its efficiency in lowering volatile organic compounds (VOCs) and formaldehyde (HCHO). The results shown that a MopFan with rotary mop constructed with Coco fibres and utilising UVC light achieves the best VOC and HCHO purification performance. Within 2 h, this combination lowered HCHO by 50% and VOCs by 23% approximately.

Assessment of Mobile Air Cleaners to Reduce the Concentration of Infectious Aerosol Particles Indoors

Airborne transmission via aerosol particles without close human contact is a possible source of infection with airborne viruses such as SARS-CoV-2 or influenza. Reducing this indirect infection risk, which is mostly present indoors, requires wearing adequate respiratory masks, the inactivation of the viruses with radiation or electric charges, filtering of the room air, or supplying ambient air by means of ventilation systems or open windows. For rooms without heating, ventilation, and air conditioning (HVAC) systems, mobile air cleaners are a possibility for filtering out aerosol particles and therefore lowering the probability of indirect infections. The main questions are as follows: (1) How effectively do mobile air cleaners filter the air in a room? (2) What are the parameters that influence this efficiency? (3) Are there room situations that completely prevent the air cleaner from filtering the air? (4) Does the air cleaner flow make the stay in the room uncomfortable? To answer these questions, particle imaging methods were employed. Particle image velocimetry (PIV) was used to determine the flow field in the proximity of the air cleaner inlet and outlet to assess regions of unpleasant air movements. The filtering efficiency was quantified by means of particle image counting as a measure for the particle concentration at multiple locations in the room simultaneously. Moreover, different room occupancies and room geometries were investigated. Our results confirm that mobile air cleaners are suitable devices for reducing the viral load indoors. Elongated room geometries, e.g., hallways, lead to a reduced filtering efficiency, which needs to be compensated by increasing the volume flow rate of the device or by deploying multiple smaller devices. As compared to an empty room, a room occupied with desks, desk separation walls, and people does not change the filtering efficiency significantly, i.e., the change was less than 10%. Finally, the flow induced by the investigated mobile air cleaner does not reach uncomfortable levels, as by defined room comfort standards under these conditions, while at the same time reaching air exchange rates above 6, a value which is recommended for potentially infectious environments.

Unwanted Indoor Air Quality Effects from Using Ultraviolet C Lamps for Disinfection

Ultraviolet germicidal irradiation (UVGI) is known to inactivate various viruses and bacteria, including SARS-CoV-2, and is widely applied especially in medical facilities. This inactivation results from the high photon energies causing molecular bonds to break, but when nonpathogen molecules are affected, unwanted effects may occur. Here, we explored the effect of a commercial high intensity (similar to 2 kW) UVC disinfection device on the composition and concentration of gases and particles in indoor air. We find that the UVC (254 nm) caused dramatic increases in particle number concentrations, and nearly all (similar to 1000) monitored gas phase species also increased. These responses were unsurprising when considering the typical impacts of UVC on atmospheric chemistry. High particle concentrations are associated with adverse health effects, suggesting that the impact of UVGI devices on indoor air quality (IAQ) should be studied in much more detail. The high-intensity device in this study was intended for short durations in unoccupied rooms, but lower-intensity devices for continuous use in occupied rooms are also widely applied. This makes further studies even more urgent, as the potential IAQ effects of these approaches remain largely unexplored.

Unwanted Indoor Air Quality Effects from Using Ultraviolet C Lamps for Disinfection

Ultraviolet germicidal irradiation (UVGI) is known to inactivate various viruses and bacteria, including SARS-CoV-2, and is widely applied especially in medical facilities. This inactivation results from the high photon energies causing molecular bonds to break, but when nonpathogen molecules are affected, unwanted effects may occur. Here, we explored the effect of a commercial high-intensity (∼2 kW) UVC disinfection device on the composition and concentration of gases and particles in indoor air. We find that the UVC (254 nm) caused dramatic increases in particle number concentrations, and nearly all (∼1000) monitored gas phase species also increased. These responses were unsurprising when considering the typical impacts of UVC on atmospheric chemistry. High particle concentrations are associated with adverse health effects, suggesting that the impact of UVGI devices on indoor air quality (IAQ) should be studied in much more detail. The high-intensity device in this study was intended for short durations in unoccupied rooms, but lower-intensity devices for continuous use in occupied rooms are also widely applied. This makes further studies even more urgent, as the potential IAQ effects of these approaches remain largely unexplored. © 2023 The Authors. Published by American Chemical Society.

Estimating the restraint of SARS-CoV-2 spread using a conventional medical air-cleaning device: Based on an experiment in a typical dental clinical setting.

OBJECTIVES: Droplets or aerosols loaded with SARS-CoV-2 can be released during breathing, coughing, or sneezing from COVID-19-infected persons. To investigate whether the most commonly applied air-cleaning device in dental clinics, the oral spray suction machine (OSSM), can provide protection to healthcare providers working in clinics against exposure to bioaerosols during dental treatment. METHOD: In this study, we measured and characterized the temporal and spatial variations in bioaerosol concentration and deposition with and without the use of the OSSM using an experimental design in a dental clinic setting. Serratia marcescens (a bacterium) and ΦX174 phage (a virus) were used as tracers. The air sampling points were sampled using an Anderson six-stage sampler, and the surface-deposition sampling points were sampled using the natural sedimentation method. The Computational Fluid Dynamics method was adopted to simulate and visualize the effect of the OSSM on the concentration spatial distribution. RESULTS: During dental treatment, the peak exposure concentration increased by up to 2-3 orders of magnitude (PFU/m3) for healthcare workers. Meanwhile, OSSM could lower the mean bioaerosol exposure concentration from 58.84 PFU/m3 to 4.10 PFU/m3 for a healthcare worker, thereby inhibiting droplet and airborne transmission. In terms of deposition, OSSM significantly reduced the bioaerosol surface concentration from 28.1 PFU/m3 to 2.5 PFU/m3 for a surface, effectively preventing fomite transmission. CONCLUSION: The use of OSSM showed the potential to restraint the spread of bioaerosols in clinical settings. Our study demonstrates that OSSM use in dental clinics can reduce the exposure concentrations of bioaerosols for healthcare workers during dental treatment and is beneficial for minimizing the risk of infectious diseases such as COVID-19.

Large-scale evaluation of microorganism inactivation by bipolar ionization and photocatalytic devices.

The COVID-19 pandemic has raised awareness in the spread of disease via airborne transmission. As a result, there has been increasing interest in technologies that claim to reduce concentrations of airborne pathogens in indoor environments. The efficacy of many of these emerging technologies is not fully understood, and the testing that has been done is often conducted at a small scale and not representative of applied settings. There is currently no standard test method for evaluating air treatment technologies, making it difficult to compare results across studies or technology types. Here, a consistent testing approach in an operational-scale test chamber with a mock recirculating heating, ventilation, and air conditioning (HVAC) system was used to evaluate the efficacy of bipolar ionization and photocatalytic devices against the non-enveloped bacteriophage MS2 in the air and on surfaces. Statistically significant differences between replicate sets of technology tests and control tests (without technologies active) are apparent after 1 h, ranging to a maximum of 0.88 log10 reduction for the bipolar ionization tests and 1.8 log10 reduction for the photocatalytic device tests. It should be noted that ozone concentrations were elevated above background concentrations in the test chamber during the photocatalytic device testing. No significant differences were observed between control and technology tests in terms of the amount of MS2 deposited or inactivated on surfaces during testing. A standardized, large-scale testing approach, with replicate testing and time-matched control conditions, is necessary for contextualizing laboratory efficacy results, translating them to real-world conditions, and for facilitating technology comparisons.

Continuous air cleaning by filtration and UV-C treatment of airborne pathogens and particulate matter in indoor spaces

Since COVID-19 became a global pandemic, improving air quality has been increasingly important to mitigate the transmission of pathogenic aerosols. Air filters such as MERV filters have been widely used in heating, ventilation, and air conditioning (HVAC) systems to clean inlet air. In recent years, ultraviolet (UV) light has been used for decontamination and disinfection in various applications, including indoor air cleaning, e.g., upper-room ultraviolet germicidal irradiation (UVGI). There are a variety of air purification devices available in the market, with some incorporating UV technology. However, many of them are not formally tested and certified for their effectiveness in mitigating airborne pathogens and particulate matter. The research's objectives are to (1) evaluate, design, and upgrade an existing air filtration device (~2,200 CFM) with the addition of UV-C lamps;(2) test the effectiveness of the upgraded device in mitigating airborne pathogens (bacteria) and particulate matter (PM) in real scenario (poultry farm). The testing results of air quality are expressed in particular matter (PM) levels and colony-forming units (CFUs). The preliminary data showed that both MERV-8 & MERV 13 and UV-C lamps can inactivate up to 100% of airborne bacteria, and the device can remove over 95% of total PM after treatment in a ~150-layer room. © 2022 ASABE. All Rights Reserved.

Pandemic management requires exposure science.

COVID-19 was first detected in Wuhan, China, on 8.12.2019, and WHO announced it a pandemic on 11.3.2020. No vaccines or medical cures against COVID-19 were available in the first corona year. Instead, different combinations of generic non-pharmaceutical interventions - to slow down the spread of infections via exposure restrictions to 'flatten the curve' so that it would not overburden the health care systems, or to suppress the virus to extinction - were applied with varying levels of strictness, duration and success in the Pacific and North Atlantic regions. Due to an old misconception, almost all public health authorities dismissed the possibility that the virus would be transmitted via air. Opportunities to reduce the inhalation exposure - such as wearing effective FFP2/N95 respirators, improving ventilation and indoor air cleaning - were missed, and instead, hands were washed and surfaces disinfected. The fact that aerosols were acknowledged as the main route of COVID-19 transmission in 2021 opened avenues for more efficient and socially less disruptive exposure and risk reduction policies that are discussed and evaluated here, demonstrating that indoor air and exposure sciences are crucial for successful management of pandemics. To effectively apply environmental and personal exposure mitigation measures, exposure science needs to target the human-to-human exposure pathways of the virus.

Experimental Investigation of a MopFan-Based Photocatalytic Air Purification Device

Photocatalytic oxidation (PCO) is a potential approach for air cleaning, especially when utilising titanium dioxide (TiO2). A MopFan is similar to a roller brush but is made of flexible fibres coated with TiO2. Unlike conventional filter/mesh UV systems, a MopFan provides a wide UV-TiO2 interaction surface area and airflow passage. This revolutionary technique can be low cost, efficient, and potentially effective against viruses, making it suitable for cleaning indoor air. It is easy to use but technically advanced. The system may be mounted on walls, floors, or placed on desktops. A photocatalytic air purification based on MopFan prototype was designed, constructed and tested. This study utilised copper wires (0.1 mm, 0.3 mm, 0.4 mm, and 0.5 mm), plastic fibres (0.5 mm and 1.1 mm), brass wire (0.4 mm), steel wire (0.38 mm), and organic “coco” fibres (0.4 mm). Copper wire (0.5 mm) and organic fibre (0.4 mm) were found to be effective against SARS-CoV-2, but brass (0.4 mm) and plastic (0.5 mm) fibres were found only partially effective. The purification performance was compared using MopFan with plastic (0.5 mm), brass (0.4 mm) and organic “coco” (0.4 mm) fibres but the other materials were rejected due to their poor qualities or difficulties in manufacturing. It was found that the system has a better effectiveness with organic fibres, around 21% of reduction consistently throughout the test. It was also found that by using the photocatalytic MopFan air cleaning system, the final concentration of pollutants in a room is determined by the rate and concentration of pollutant generation. Highlights 1. Organic fibres do not require sanding prior to being coated with TiO2 solution. 2. Copper and organic fibres are effective SARS-CoV-2 inhibitors. 3. Organic fibres are the most efficient for air purification. 4. The performance of purification is related to the concentration of pollutants. © 2022 The Author(s).

Interpreting Air Cleaner Performance Data

The global COVID-19 pandemic has prompted widespread demand for air cleaning technologies aimed at reducing risks of airborne pathogen transmission inside buildings. The commercial landscape for air cleaning devices is complex, ranging from conventional technologies such as high-efficiency fibrous-media filters and ultraviolet germicidal irradiation (UVGI) to a wide variety of electronic air cleaning technologies such as plasma generators, hydroxyl radical generators, ionizers, photocatalytic oxidizers and others. This article demonstrates some frequently prevalent issues in electronic air cleaner performance testing and reporting and proposes a path forward to meet research needs and improve test methods that could reduce the current uncertainty about the performance of electronic air cleaning technologies. It also provides tools to support practitioners and consumers in their decision-making regarding air cleaning technologies. Copyright 2022 ASHRAE.

Combating with poor Indoor air quality to improve work environment at IndianOil

Introduction: Indoor air quality have a great impact on physical and psychological health of employees working in buildings. IndianOil Institute of Petroleum Management (IiPM), located in National Capital Region of Delhi(NCR) is a premiere institute consisting of multiple training halls & auditoriums. In view of COVID-19 pandemic, modifications were carried out in air handling unit system at IiPM. Materials and methods: A detailed study of air movements, intake and return path was carried to find out measures to ensure adequate air exchanges. Additional air inlets with Dual PM10 filters were fixed on all air intake paths to reduce the pollutant level in air entering the building. The air handling unit at the institute was also fitted with special grade air filter for bringing down the PM2.5 level below 60. Special grade filters filtered the pollutants and reduced the pollutant level of air. An online air image sensor was installed to measure the quality of ambient air after filtration. Stand-alone air cleaner/filter units were also installed in training halls, lobbies and waiting areas. Result: Following modifications there was improvement in air quality by 90%. This resulted in building confidence level and provided a stress-free safe environment for employees working at the institute. Employees working at IiPM confirmed reduction in eye irritation, headaches and fatigue due to air pollution. Discussion: Installation of air filters inside the building helps in improving air quality which in turn prevents common health issues at workplace. This has prompted us to provide similar solutions in other office buildings in NC

Antimicrobial Activity in the Gasphase with Hypochloric Acid

Background:The study investigated if the disinfecting potential of Hypochlorous acid (HOCl) in suspensions are transferrable to in-air cleaning applications and to what extent aerosolized HOCl solutions can deactivate indoor microbial contaminations in-air at or below legal limits. Material and Method: For the liquid disinfection we used a standard suspension disinfection test protocol. For the in-air tests we conducted several experiments where aerosolized bacterial suspensions were injected into lab chambers preloaded with different HOCl gas concentrations. Results:In suspension experiments we found sufficient efficacies for all studied organisms at minimum concentrations of 200 ppm HOCl. The in-air measurement set-up allows to follow microbe deactivation by HOCl interaction. The deactivation rate increases with the HOCl concentration, and the values are highest for Gram-negative bacteria. Conclusion:We confirmed our hypothesis of the high disinfecting power of HOCl in-air at safe levels for populated indoor places. The investigated bacteria provide a model system for infectious particles, including enveloped viruses (to which Coronavirus belongs). These early results suggest that HOCl should be further evaluated as an air-cleaning method which may complement established concepts. © 2021 by Walter de Gruyter Berlin/Boston.

Unintended Consequences of Air Cleaning Chemistry.

Amplified interest in maintaining clean indoor air associated with the airborne transmission risks of SARS-CoV-2 have led to an expansion in the market for commercially available air cleaning systems. While the optimal way to mitigate indoor air pollutants or contaminants is to control (remove) the source, air cleaners are a tool for use when absolute source control is not possible. Interventions for indoor air quality management include physical removal of pollutants through ventilation or collection on filters and sorbent materials, along with chemically reactive processes that transform pollutants or seek to deactivate biological entities. This perspective intends to highlight the perhaps unintended consequences of various air cleaning approaches via indoor air chemistry. Introduction of new chemical agents or reactive processes can initiate complex chemistry that results in the release of reactive intermediates and/or byproducts into the indoor environment. Since air cleaning systems are often continuously running to maximize their effectiveness and most people spend a vast majority of their time indoors, human exposure to both primary and secondary products from air cleaners may represent significant exposure risk. This Perspective highlights the need for further study of chemically reactive air cleaning and disinfection methods before broader adoption.

Engineering Solutions for Preventing Airborne Transmission in Hospitals with Resource Limitation and Demand Surge.

Among the various strategies for the prevention of airborne transmission, engineering measures are placed high in the hierarchy of control. Modern hospitals in high-income countries have mechanical systems of building ventilation also called HVAC (heating, ventilation, and air-conditioning) but installation and maintenance of such systems is a challenging and resource-intensive task. Even when the state-of-the-art technology was used to build airborne infection isolation rooms (AIIRs), recommended standards were often not met in field studies. The current coronavirus disease-2019 pandemic has highlighted the need to find cost-effective and less resource-intensive engineering solutions. Moreover, there is a need for the involvement of interdisciplinary teams to find innovative infection control solutions and doctors are frequently lacking in their understanding of building ventilation-related problems as well as their possible solutions. The current article describes building ventilation strategies (natural ventilation and hybrid ventilation) for hospitals where HVAC systems are either lacking or do not meet the recommended standards. Other measures like the use of portable air cleaning technologies and temporary negative-pressure rooms can be used as supplementary strategies in situations of demand surge. It can be easily understood that thermal comfort is compromised in buildings that are not mechanically fitted with HVAC systems, therefore the given building ventilation strategies are more helpful when climatic conditions are moderate or other measures are combined to maintain thermal comfort. HOW TO CITE THIS ARTICLE: Zia H, Singh R, Seth M, Ahmed A, Azim A. Engineering Solutions for Preventing Airborne Transmission in Hospitals with Resource Limitation and Demand Surge. Indian J Crit Care Med 2021;25(4):453-460.