Personalized Ventilation Design For Sleep Environment Of An Infant

Sudden Infant death Syndrome (SIDS) is the leading cause for the death of the infantsaged1-12months. According to previous epidemiological studies, SIDS can be associatedwith the ambient environmental factors, such as deteriorated thermal comfort, insufficientsupply of fresh air and exposure to air pollution. As infants are at the high risk for SIDSduring sleep, there is an extremely important practical significance for reducing SIDS risk, tocontrol sleep environment with effective ventilation means by directly sending adequate cleanair with appropriate temperature to the infants’ breathing zone.First, this study showed the necessity to apply personalized ventilation (PV) on aninfant’s sleep environment, by the field investigation of the quality of sleep environment.Next, to avoid thermal discomfort by air draft, we proposed wide-cover type PV (WCPV) anddisplacement type PV (DPV) to control sleep environment for infants. With WCPV, cold air issent toward the space above infant head, and then falls down by gravity to the area involvingthe head; with DPV, cold air is sent toward infant head with a very low speed, then graduallydisplaces the air around the head and penetrates into the infant’s breathing zone.Based on a validated numerical method based on Computational Fluid Dynamics (CFD),this study investigated the performance of aforementioned two PVs. In the numerical modelof indoor environment, the infant slept in a supine position on the bed in the middle of theroom; an air-conditioner mounted on the wall behind the bed blown air of24oC downward ata45°angle at a speed of0.4m/s, and resulted in an air change rate of5ACH; a PV unit0.1m away from the bed supplied clean air of18oC at an airflow rate of0.5L/s. According to thesimulation results, while using WCPV and DPC, the conditions in the area around the headwere consistent with the infant’s requirement for thermal comfort with wind speeds under0.2m/s and air temperatures varying between18~22oC. On the other hand, compared to the casewithout using PV, the mean age of air in the infant’s breathing zone decreased by39%withWCPV and by86%with DPV. Compared with the case using WCPV, the clean air from DPVreached the infant’s breathing zone4.6times faster, and accessibility of supply air increasedby24%. In addition, this study investigated the impacts on the infant of the third-hand smokeand influenza from an adult standing beside the bed opposite to the PV unit. According to the results, the concentration of third-hand smoke in the infant’s inhalation decreased by67%with WCPV and86%with DPV, and the risk of influenza infection decreased by68%withWCPV and92%with DPV.Furthermore, this study examined the effect of amount of air supply by the PVs and sleepposition of the infant, on the performance of the PVs. After the airflow rate of personalized airwas cut in half from0.5L/s to0.25L/s, ventilation effectiveness declined obviously in theinfant’s breathing zone with great increase in the exposure to indoor air pollution. When theinfant slept at his side with the face toward the opposite side of the PV unit, the performanceof WCPV was improved but still inferior to that of DPV.In conclusion, compared to WCPV, the application effect of DPV is superior to WCPV.DPV indicated a much better performance on the control of the quality of inhalation.