Carbon Dioxide Monitoring in Refuse Collection Vehicle Cabins to Reduce the Risk of SARS-CoV-2 Airborne Transmission

During the COVID-19 pandemic, essential workers such as waste collection crews continued to provide services in the UK, but due to their small size, maintaining social distancing inside waste collection vehicle cabins is impossible. Ventilation in cabins of 11 vehicles operating in London was assessed by measuring air supply flow rates and carbon dioxide (CO2) in the driver's cabin, a proxy for exhaled breath. The indoor CO2 indicated that air quality in the cabins was mostly good throughout a working day. However, short episodes of high CO2 levels above 1500 ppm did occur, mainly at the beginning of a shift when driving towards the start of their collection routes. This data indicated that the ventilation systems on the vehicles were primarily recirculating air and the fresh air supply made up only 10-20 % of the total airflow. Following recommendations to partly open windows during shifts and to maintain ventilation systems, a second monitoring campaign was carried out, finding on average, an improvement in ventilation on board the vehicles. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Predicting the infection probability distribution due to airborne and droplet transmission

In this study, a method was proposed to predict the infection probability distribution rather than the room-averaged value. The infection probability by airborne transmission was predicted based on the CO2 concentration. The infection probability by droplet transmission was predicted based on occupant position information. Applying the proposed method to an actual office confirmed that it could be used for quantitatively predicting the infection probability by integrating the ventilation efficiency and distance between occupants. The infection probability by airborne transmission was relatively high in a zone where the amount of outdoor air supply was relatively small. The infection probability by droplet transmission varied with the position of the occupants. The ability of the proposed method to analyze the relative effectiveness of countermeasures for airborne transmission and droplet transmission was verified in this study. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Use of Micrococcus luteus to assess the quality of protection of respiratory organs using the pneumatic helmet with positive airflow.

In order to effectively protect from dangerous infectious agents, as well as coronavirus, the scientists of I. Horbachevsky Ternopil national medical university (Ukraine) developed a unique prototype of a mobile respiratory protection system with positive airflow - pneumatic helmet. AIM: To evaluate the bacterial permeability of the proposed concept model of the pneumohelmet in full and partial configuration. MATERIALS AND METHODS: With a generating device (compressor inhaler) an aerosol is created from bacterial suspension, which is directed to the inlet of the personal protective respiratory equipment. The outlet is directed at a Petri dish with meat-peptone broth. Evaluation of bacterial contamination is performed by calculating the colony-forming units by multiplying the indicator by the degree of dilution. The study is repeated with a partial configuration of the pneumatic helmet - the presence of only external, only internal filter or not using any filter components. RESULTS: The growth of Micrococcus luteus colonies on the placed nutrient medium when using the proposed conceptual model of the pneumatic helmet in full configuration was not obtained. Removal of the inner filter did not lead to a violation of the effectiveness of antibacterial protection, as bacteria were detected only on the outer side of filter No.2. The use of a conceptual model without filters made it possible to detect colonies of Micrococcus luteus on the medium and components of the device with the calculation of colony forming units in 3- and 4-fold dilutions. During 24 hours of operation, the bacterial load on the surface of the external filter increased significantly. However, no signs of malfunction of the pneumatic helmet were detected. CONCLUSIONS: The given results confirm the ability of the pneumatic helmet to counteract the penetration of bacteria from the environment during 6, 12, 24 hours of continuous operation. The protection was preserved even with partial configuration, which indicates the presence of a margin of reliability of this system.

Numerical simulation of air distribution in the consultation room of patients with novel coronavirus

The hospital room is the first line of assistance to patients, to ensure the comfort of doctors and patients at the same time, but also to ensure the protection of the personal safety of doctors and patients. For this reason, a good airflow organization helps to reduce the concentration of respiratory particles in the whole space and also creates a comfortable environment. Based on the CFD theory of computational fluid dynamics, ANSYS Fluent software is used to simulate the clinic environment, and four airflow organizations are used as the research objects, and the temperature cloud map, air age, and draft rate (DR) are used as the evaluation indexes, while the particulate matter concentration in the clinic is analyzed, and the 10 main indexes for evaluating the clinic environment are subjected to the principal component analysis algorithm (PCA), the four airflow organizations are comprehensive ranking. Since the traditional questionnaire has a lot of human subjectivity, using the algorithm can effectively compensate for the shortcomings of the questionnaire, and comparing the conclusions derived from the PCA algorithm with the results of the questionnaire can make the conclusions more scientific. The final conclusion is that the airflow organization of the replacement air supply can meet human comfort and air freshness while reducing the concentration of respiratory particulate matter in the clinic environment under the evaluation of various indexes, for which the replacement air supply scheme can provide a theoretical basis and reference for future construction implementation. © 2022 SPIE.

How to Cover Additional Cooling Load Needs During COVID-19 Pandemic?

It has been crystal clear to everyone that the fresh air supply is one of the highest priorities to keep people under safe indoor conditions during the COVID-19 pandemic. In many buildings, either there are no mechanical ventilation systems or the air conditioning systems do not have adequate capacity to meet the additional cooling loads for the increased fresh air requirement. Providing fresh air without disturbing the thermal conditions in the building requires a substantially increased cooling load and operating costs. On the other hand, there may not be adequate power infrastructure to meet this additional energy demand item in many regions. In this technical brief paper, we aim to emphasize the importance of heat storage systems and provide a quick solution to illustrate that they can meet the fresh air demands without requiring additional chiller or chiller capacity. In addition, it is observed that heat storage systems can be a convenient solution to meet the urgent and additional cooling loads in a more sustainable way.

Integrated system of exhaust air heat pump and advanced air distribution for energy-efficient provision of outdoor air.

A large outdoor air supply is required to control the airborne infection risk of respiratory diseases (e.g., COVID 19) but causes a high energy penalty. This study proposes a novel integrated system of the exhaust air heat pump and advanced air distribution to energy-efficiently provide outdoor air. The system energy performances are evaluated by the experimentally validated thermodynamic model of heat pump and heat removal efficiency model of advanced air distribution. Results show the exhaust air heat pump with advanced air distribution can save energy because of three mechanisms. First, the exhaust air heat pump reuses the exhaust air to reduce the condensation temperature, thereby improving the coefficient of performance. Second, advanced air distribution reduces ventilation load. Third, advanced air distribution reduces the condensation temperature and enhances the evaporation temperature, thereby improving the coefficient of performance. The exhaust air heat pump saves energy by 18%, advanced air distribution saves energy by 36%, and the integrated system of the exhaust air heat pump and advanced air distribution can save energy by 45%. As a specific application, compared with the conventional system (i.e., the outdoor air heat pump with mixing ventilation), the exhaust air heat pump with stratum ventilation saves energy by 21% - 35% under various outdoor air ratios and outdoor air temperatures. The proposed integrated system of the exhaust air heat pump and advanced air distribution contributes to the development of low-carbon and healthy buildings.

Evaluating risk of SARS-CoV-2 infection of the elderly in the public bus under personalized air supply.

In developing countries, public transportation is the first choice for the elderly because of its convenience and cheapness. The high density population of public transportation increases the risk of passengers contracting infectious diseases, so it is extremely critical to determine healthy transportation systems to safeguard the health of passengers. The propagation characteristics of droplets in the ZK-type public bus were studied by computational fluid simulation employing the Realizable k-ε turbulence model and discrete phase model. The modified Wells-Riley model was used to quantitatively assess the infection risk of SARS-CoV-2 spread by droplets on the elderly. The risk assessment shows that when the personalized air supply angle is 30°, the number of infected passengers is the least, reaching 14, which shows that the infection risk of passengers can be reduced through the design of personalized air supply angle. Regardless of the angle of the personalized air supply, the rear seats are in a low-risk area. Therefore, it's recommended that elderly passengers choose the rear seats of the public bus during the epidemic to prevent being infected. This study can provide a reference for healthy transportation systems to construct a healthy environment inside the public bus.

Effects of Air Supply Terminal Devices on the Performance of Variable Refrigerant Flow Integrated Stratum Ventilation System: An Experimental Study

A variable refrigerant flow integrated stratum ventilation (VRF-SV) system was proposed as an energy efficient substitute for conventional central cooling systems for buildings. The novel system provided conditioned air to enclosed spaces with high indoor air quality and thermal comfort. This study investigated the effects of different types of ASTDs on the performance of the VRF-SV hybrid system. The performance was experimentally evaluated with five air terminal types, including bar grille, double deflection grille, jet slot, perforated and drum louver diffusers. The evaluation was carried out using standard indices: temperature and velocity distribution, airflow pattern, effective draft temperature (EDT), air distribution performance index (ADPI), thermal sensation vote and comfort feedback survey. The results indicated that the ASTD type had a significant impact on airflow pattern. Furthermore, the bar grille diffuser provided the occupants with greater thermal comfort and acceptable indoor environment. Almost all the EDT values determined in the breathing zone in the case with bar grille diffuser found under the satisfactory range, i.e., −1.2 < K < 1.2. Based on these values, the ADPI for bar grille diffuser was calculated as 92.8%. Thus, the bar grille diffuser is recommended to be installed with the VRF-SV hybrid system in buildings.

Simulation Studies Provide Evidence of Aerosol Transmission of SARS-CoV-2 in a Multi-Story Building via Air Supply, Exhaust and Sanitary Pipelines.

A cross-layer non-vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) occurred in a quarantine hotel in Guangzhou, Guangdong Province, China in June 2021. To explore the cross-layer transmission path and influencing factors of viral aerosol, we set up different scenarios to carry out simulation experiments. The results showed that the air in the polluted room can enter the corridor by opening the door to take food and move out the garbage, then mix with the fresh air taken from the outside as part of the air supply of the central air conditioning system and re-enter into different rooms on the same floor leading to the same-layer transmission. In addition, flushing the toilet after defecation and urination will produce viral aerosol that pollutes rooms on different floors through the exhaust system and the vertical drainage pipe in the bathroom, resulting in cross-layer vertical transmission, also aggravating the transmission in different rooms on the same floor after mixing with the air of the room and entering the corridor to become part of the air supply, and meanwhile, continuing to increase the cross-layer transmission through the vertical drainage pipe. Therefore, the air conditioning and ventilation system of the quarantine hotel should be operated in full fresh air mode and close the return air; the exhaust volume of the bathroom should be greater than the fresh air volume. The exhaust pipe of the bathroom should be independently set and cannot be interconnected or connected in series. The riser of the sewage and drainage pipeline of the bathroom should maintain vertical to exhaust independently and cannot be arbitrarily changed to horizontal pipe assembly.