Conceptual Design of a UVC-LED Air Purifier to Reduce Airborne Pathogen Transmission—A Feasibility Study

Existing indoor closed ultraviolet-C (UVC) air purifiers (UVC in a box) have faced technological challenges during the COVID-19 breakout, owing to demands of low energy consumption, high flow rates, and high kill rates at the same time. A new conceptual design of a novel UVC-LED (light-emitting diode) air purifier for a low-cost solution to mitigate airborne diseases is proposed. The concept focuses on performance and robustness. It contains a dust-filter assembly, an innovative UVC chamber, and a fan. The low-cost dust filter aims to suppress dust accumulation in the UVC chamber to ensure durability and is conceptually shown to be easily replaced while mitigating any possible contamination. The chamber includes novel turbulence-generating grids and a novel LED arrangement. The turbulent generator promotes air mixing, while the LEDs inactivate the pathogens at a high flow rate and sufficient kill rate. The conceptual design is portable and can fit into ventilation ducts. Computational fluid dynamics and UVC ray methods were used for analysis. The design produces a kill rate above 97% for COVID and tuberculosis and above 92% for influenza A at a flow rate of 100 L/s and power consumption of less than 300 W. An analysis of the dust-filter performance yields the irradiation and flow fields.

From Guidance to Implementation: Applying ASHRAE Epidemic Task Force Building Readiness Strategies in 95 Commercial Office Buildings

During the COVID-19 pandemic, building owners and operators sought to protect their occupants by following ASHRAE and CDC guidance for HVAC and water system risk mitigation. This paper presents the results of building readiness assessments conducted for 95 commercial office buildings across the United States. In these assessments, the authors evaluated buildings for initial alignment with ASHRAE Epidemic Task Force (ETF) guidance and recommended action where additional risk mitigation measures were warranted. The engineering assessments focused on outdoor air ventilation rates, filtration efficiency levels, flushing spaces during unoccupied periods, and Eegonella water management practices. Primary challenges to implementing ETF guidance included resistance to operational changes with potential adverse energy impacts, concerns regarding existing system limitations, and in a limited number of cases, ventilation system design constraints. The assessments showed that most of the office buildings could modify their HVAC and water system operatingpractices to minimize the spread of harmful pathogens without major upgrades to equipment or significant increases in energy use. Almost all subject buildings had the capacity to meet or exceed minimum ventilation rates, upgrade to at least MERV-13 filters, implement appropriate flushing periods to achieve target clean air changes, and manage their water systems to minimize Legionella risk.

A Review of Selected Types of Indoor Air Purifiers in Terms of Microbial Air Contamination Reduction

Aims: With the ongoing pandemic and increased interest in measures to improve indoor air quality, various indoor air purifiers have become very popular and are widely used. This review presents the advantages and disadvantages of various types of technologies used in air purifiers in terms of reducing microbial contamination. Methods: A literature search was performed using Web of Science, Scopus, and PubMed, as well as technical organizations dealing with indoor air-quality to identify research articles and documents within our defined scope of interest. Relevant sections: The available literature data focus mainly on the efficiency of devices based on tests conducted in laboratory conditions with test chambers, which does not reflect the real dimensions and conditions observed in residential areas. According to a wide range of articles on the topic, the actual effectiveness of air purifiers is significantly lower in real conditions than the values declared by the manufacturers in their marketing materials as well as technical specifications. Conclusions: According to current findings, using indoor air purifiers should not be the only measure to improve indoor air-quality;however, these can play a supporting role if their application is preceded by an appropriate technical and environmental analysis considering the real conditions of its use.

Personalized Ventilation as a Possible Strategy for Reducing Airborne Infectious Disease Transmission on Commercial Aircraft

Featured ApplicationPersonalized ventilation systems for improving air quality around passengers in confined vehicles, such as airplanes.In the last decade, there has been an increase in ease and affordability of air travel in terms of mobility for people all around the world. Airplane passengers may experience different risks of contracting airborne infectious diseases onboard aircraft, such as influenza or severe acute respiratory syndrome (SARS-CoV-1 and SARS-CoV-2), due to nonuniform airflow patterns inside the airplane cabin or proximity to an infected person. In this paper, a novel approach for reducing the risk of contracting airborne infectious diseases is presented that uses a low-momentum personalized ventilation system with a protective role against airborne pathogens. Numerical simulations, supported by nonintrusive experimental measurements for validation purposes, were used to demonstrate the effectiveness of the proposed system. Simulation and experimental results of the low-momentum personalized ventilation system showed the formation of a microclimate around each passenger with cleaner and fresher air than produced by the general mixing ventilation systems.