Sleep must be protected against aggressions and manipulations, made voluntarily or not, which tend to reduce its duration to the benefit of prolonged waking state. Sleep disturbances have various origins but only external factors of our environment, such as noise and extreme thermal ambient conditions, will be considered here. These disturbance factors generally lead to increasing the waking time and time spent in shallow sleep stages and to reducing time spent in slow wave sleep and REM-sleep. The consequences of these disturbances are mainly seen during the consecutive waking period. The sensation of fatigue due to the lack of sleep and the associated low vigilance level, together with the deterioration of mood and performance, modify the person’s attitudes and in some cases can lead to serious consequences in terms of accident risks.