A single-blind field intervention study of whether increased bedroom ventilation improves sleep quality.

A four-week-long field intervention experiment was conducted in twenty-nine bedrooms with extract ventilation systems and air inlet vents. During the first week no interventions took place. In the three weeks that followed, each participant slept for one week under a low, moderate, and high ventilation rate condition in a balanced order. These conditions were established by covertly altering the fan speed of the exhaust ventilation system without changing other settings. Participants were not informed when or even whether the changes to bedroom ventilation would be executed. The bedroom environmental quality was monitored continuously and sleep quality was monitored using wrist-worn trackers. Tests of cognitive performance were conducted in the evening and morning. In twelve bedrooms where clear differences between the three ventilation conditions occurred, as indicated by the measured CO2 concentrations, participants had significantly less deep sleep, more light sleep and more awakenings at lower ventilation rate conditions. In twenty-three bedrooms where a clear difference in ventilation rate between the high and low ventilation conditions was observed, as confirmed by the measured CO2 concentrations, the deep sleep was significantly shorter in the low ventilation rate condition. No differences in cognitive performance between conditions were observed. At lower ventilation rate conditions, the concentrations of CO2 increased, as did the relative humidity, while bedroom temperatures remained unchanged. The present results, which were obtained in actual bedrooms, confirm the findings in previous studies of a positive effect of increased ventilation on sleep quality. Further studies with larger populations and better control of bedroom conditions, particularly ventilation, are required.

Forward scattering induced by water drops on a transmissive substrate.

In this study the scattering of radiation by condensation drops deposited on a single glass plate is dealt with. Experiments were carried out in the visible radiation range by means of a laboratory measuring unit as a function of three parameters, namely, the phase of the condensation process, the wavelength of the incident radiation, and the radiation incidence angle. The experiments indicated that during the condensation process a steady state in the scattering pattern of single glass occurred after a transition phase. Owing to the condensate, more than 80% of the transmitted visible radiation was scattered. The scattering slightly diminished with increasing wavelength, from 400 to 700 nm, and the asymmetry of the scattering pattern enlarged with increasing incidence angle of the radiation.