Fume hoods are an indispensable instrument for experimental operations dealing with hazardous chemicals, wherein safety operations are strictly adherent to regulations. Within this context, few cases exist wherein the ventilation efficiency and pollutant capture efficiency inside fume hoods are precisely analyzed and quantitatively visualized. In this study, the pollutant capture efficiencies of a fume hood were analyzed by computational fluid dynamics as functions of exhaust airflow rate and according to the posture of workers in front of the fume hood. The indices for ventilation efficiencies, that is, age of air (SVE3), net escape velocity (NEV), and local purging flow rate (L-PFR), were adopted to quantitatively evaluate the pollutant concentration distributions formed inside the fume hood. NEV analysis revealed that the presence of a worker at the front of the fume hood did not significantly affect the pollutant capture efficiency at the opening surface of the fume hood. Changing the exhaust airflow rate resulted in changes in the size of the circulation flow formed in the upper part of the chamber. The circulation flow was found to have a dominant effect on the distribution of SVE3 and on the formation of the pollutant concentration distribution in the chamber.

The establishment of a healthy indoor environment requires the accurate evaluation of an individual’s exposure to pollutants. The concentration of indoor chemical pollutants is a representative indicator for such evaluation and is generally measured on-site. Moreover, material flow analysis (MFA), using macroscopic statistical data, is a reasonable method for objectively evaluating pollution on a wide scale; however, no effective strategy exists for the prediction of indoor air pollution, nor for the assessment of an individual’s exposure from social stock data. Accordingly, we developed a novel integration method comprising MFA and computational fluid dynamics (CFD) with a computer-simulated person (CSP) to establish a framework for evaluating indoor pollutant concentration and individual exposure of residents. We focused on diethyl-hexyl phthalate (DEHP) and first estimated the amount of DEHP-containing product accumulation in Japan by MFA. Second, we conducted a thorough survey and measurement of DEHP emission rates. Using these results as boundary conditions for indoor CFD with CSP, the individual exposure of a resident, in a standard residential house, was quantitatively evaluated. The total daily exposure per unit of body weight was estimated to be more than 100 (μg/kg/d) in the worst-case scenario which was considered the upper limit for exposure in this analysis.

In the existing ventilation design, the ventilation rate is defined by the time‐averaged flow rate, and the fluctuating (turbulence) component is not typically considered. However, inlet turbulent conditions are also assumed to have some influence on the formation of contaminant distributions. Therefore, the influence of turbulent kinetic energy at the inlet boundary on scalar transportation in an indoor environment needs to be elucidated when discussing the ventilation rate setpoint via the supply inlet in terms of local contaminant concentration control. This study discusses the impact of turbulent kinetic energy in the ventilation design on scalar transfer and its distribution within an enclosed space. To understand the influence of various inlet turbulent boundary conditions on scalar transfer, a computational fluid dynamics analysis was conducted using two different room models: a simple room and a room with a ventilation system that creates a large velocity gradient. The results indicate that scalar transfer within the room is not solely dominated by the averaged velocity input at the inlet boundary but is also strongly affected by the turbulence conditions at the inlet boundary. The numerical results indicate the possibility of a new ventilation design strategy that simultaneously considers the transfer of turbulent components and contaminants.

The airflow balance test to confirm the physical performance of biological safety cabinets (BSC) is standardized by JIS K 3800 in accordance with NSF/ANSI 49 in Japan. In the test, Bacillus atrophaeus spores are used as an evaluation index, which poses a few limitations, such as their dependence on the environmental conditions to be tested. The aim of this study is to develop BSC digital twins and discuss reasonable alternatives for performance evaluation tests while maintaining the accuracy of the bacterial test performance. Herein, we provide the outline of a digital twin model for BSCs and the results of a numerical analysis, where a passive scalar is used as an alternative pollutant in the evaluation index.

A fume hood is a local ventilation system that is typically installed in a laboratory space to ensure the safety of workers from chemical exposure. A fume hood is designed to capture hazardous gas‐phase pollutants generated inside a box‐like enclosure, and the pollutant capture efficiency is regulated by the average opening surface air velocity. However, few cases exist in which the pollutant capture efficiency inside the fume hood is precisely analyzed and quantitatively visualized. In this study, the capture performance of a fume hood under actual use conditions was evaluated using computational fluid dynamics (CFD). The factors that could affect the performance, that is, the exhaust airflow rate, experimental instruments inside, worker in front, and heat source within the fume hood, were parametrically considered. The numerical analyses revealed that experimental instruments near the opening surface significantly affected the airflow into the fume hood and decreased its capture performance. Under the inadequate condition of a low exhaust airflow rate, pollutant leakage inside the chamber was observed due to the presence of a worker in front of the fume hood and the heat source inside. Furthermore, the pollutant capture performance was slightly improved by changing the layout/position of the experimental instrument.