Can CO2 be used as an indicator of the probability of cross-infection?

The validity of using CO2 as an indicator of airborne infection probability was studied. Tracer gas measurements were conducted in a field lab with two breathing thermal manikins resembling "infected” and "susceptible” persons seated at desks. The room was ventilated with a mixing air distribution. Experiments were performed at three ventilation rates. CO2 gas was dosed into the air exhaled by the manikins to simulate the metabolic CO2 generation by people. Simultaneously, nitrous oxide (N2O) tracer gas was dosed into the air exhaled by one of the manikins ("infected person”) to simulate the emission of exhaled infectious particles. CO2 and N2O concentrations were measured at several points. The probability of infection was calculated based on the concentration of CO2 and N2O measured in the air inhaled by the exposed manikin ("susceptible person”). The results did not confirm that CO2 can be used as a proxy to assess the infection probability. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Influence of air supply velocity and room temperature conditions on bioaerosols distribution in a class I operating room

Surgical site infections (SSIs) have gained increasing prominence in recent decades. Bioaerosols are an important factor causing such intraoperative infections. Their distribution can be affected by environmental parameters in the operating room (OR), such as the air supply velocity and room temperature. The research object of this study was a Class I operating room, which has the strictest cleanliness requirements. Four different air supply velocities (0.16, 0.24, 0.29, and 0.33 m/s) and four different room temperatures (18 °C, 20 °C, 22 °C, and 24 °C) formed seven orthogonal experiment cases. The bioaerosols release experiments conducted in an environmental chamber to simulate a full-scale operating room. The experiments could well verify the computational fluid dynamics-based numerical simulation using the renormalization group (RNG) k-ε model as a turbulence model. The experimental and numerical results confirmed that an increase in the air supply velocity would increase the dispersion of bioaerosols particles. An air supply velocity greater than 0.24 m/s can ensure greater cleanliness in the surgical area. Whereas, when the air supply velocity continues to increase (0.33 m/s), it will increase the bioaerosols deposition in the surgical area. In terms of controlling the concentration of bioaerosols in a certain area, 0.24 m/s-0.29 m/s is the optimal range of air supply velocity. However, the distribution of bioaerosols particles is not sensitive to the response of OR room temperature changes.