Experimental and simulated evaluations of airborne contaminant exposure in a room with a modified localized laminar airflow system

Abstract

The traditional mixing ventilation is not an energy effective approach to remove indoor air pollutants, maintain breath zone air quality, and control the airborne transmission. This study investigated the potential of a localized laminar airflow ventilation system to alleviate human exposure to pollutants. Breathing thermal manikins with sitting posture and supine posture were used to simulate the human. N2O was used as the tracer gas to simulate the indoor pollutants emission. The contaminant exposure index (εexp) and intake fraction index (IF) were used to assess the risk of human pollutant exposure for various supply air velocities given different emission source positions. Enhanced pollutant removal efficiency (Eff) (from the result) showed the qualification and desirability of the localized laminar airflow ventilation system in improving the breath zone air quality. The results showed that the CFD results could fit well with the experimental data, and found out the interaction between thermal plume and supply air. The results also indicated a low εexp and IF, with the 𝐸𝑓𝑓 over 90%, all of which were highly correlated with the supply velocity. Human's different breathing methods have little influence on the pollutant exposure so as to the location of the pollution source. This study found that localized laminar airflow ventilation system could efficiently provide fresh air to the breathing zone without sacrificing the thermal environment around human. It can be used for small region air quality control such as that in the bedroom and living room where desired air quality is favored.

Ventilation strategies to reduce airborne transmission of viruses in classrooms: A systematic review of scientific literature

“…Furthermore, tracer gas simulations are less complex, and no assumption or simplification are required for the modelling, thus it is easier to obtain reliable results. According to this, to simulate the exhaled virus droplet nuclei from the source manikin, breathing thermal manikins [ 49 ] are needed, while the tracer gas concentrations could be monitored and measured via a set of fast gas concentration meters [ 50 ] to evaluate the exposure risk indices ( and IF) [ 51 , 52 ].…”

Exposure of Ophthalmologists to Patients' Exhaled Droplets in Clinical Practice: A Numerical Simulation of SARS-CoV-2 Exposure Risk

“…A comparison was made between the ophthalmologist's inhalation exposure in this study and the interpersonal exposure that has been reported in previous studies. As shown in Figure 3, the previous studies were classified as CFD (17)(18)(19)(20)(21)(22) or experimental studies, where the latter used tracer gas (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33) or particles (34) to simulate droplets or droplet nuclei. In addition, Ueki (35) compared the inhalation exposure to live SARS-CoV-2 particles when wearing no mask, a surgical mask or an N95 respirator.…”

A vertical laminar airflow system to prevent aerosol transmission of SARS-CoV-2 in building space: Computational fluid dynamics (CFD) and experimental approach

“…Thus, the most effective way to mitigate the pathogenic aerosols and other bio-contaminants in buildings is to provide an appropriate method of space ventilation. 3,16,17 Raymond Tellier 18 found that supply of the clean outdoor air (OA) dilutes indoor aerosol density quickly, and Jiang et al 19 and Bartlett et al 20 investigated the control of appropriate air change rate (air change per hour, ACH) and flow velocity and direction of the supply air, which are important to reduce infection risk in all building types (e.g. office, stores and public restaurants).

Figure 1.Simulation of indoor airflow and expiration in a building space.

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