A system for monitoring the exposure of a patient to at least one environmental factor, comprising: - a receiver module for receiving a measurement signal representing a level of the environmental factor in a vicinity of the patient, - a database for storing an environmental prescription for the patient, the environmental prescription specifying a maximum level of the environmental factor and a minimum duration for the level of the environmental factor to be smaller than the maximum level, wherein the minimum duration is a minimum duration of a rest period for the patient; and - an evaluation module configured to: compare the level of the environmental factor with the maximum level on the basis of the measurement signal to determine if a rest period for the patient is ongoing, if it is determined that a rest period for the patient is ongoing, detect on the basis of the comparison a time interval in which the level of the environmental factor is substantially permanently below the maximum level, wherein the time interval is the duration of the ongoing rest period, determine a difference between a duration of the detected time interval and the minimum duration of the rest period for the patient, and control at least one output unit to output information representative of the determined difference and indicative of whether a rest period for the patient is ongoing. - a receiver module for receiving a measurement signal representing a level of the environmental factor in a vicinity of the patient, - a database for storing an environmental prescription for the patient, the environmental prescription specifying a maximum level of the environmental factor and a minimum duration for the level of the environmental factor to be smaller than the maximum level, wherein the minimum duration is a minimum duration of a rest period for the patient; and - an evaluation module configured to: compare the level of the environmental factor with the maximum level on the basis of the measurement signal to determine if a rest period for the patient is ongoing, if it is determined that a rest period for the patient is ongoing, detect on the basis of the comparison a time interval in which the level of the environmental factor is substantially permanently below the maximum level, wherein the time interval is the duration of the ongoing rest period, determine a difference between a duration of the detected time interval and the minimum duration of the rest period for the patient, and control at least one output unit to output information representative of the determined difference and indicative of whether a rest period for the patient is ongoing. compare the level of the environmental factor with the maximum level on the basis of the measurement signal to determine if a rest period for the patient is ongoing, if it is determined that a rest period for the patient is ongoing, detect on the basis of the comparison a time interval in which the level of the environmental factor is substantially permanently below the maximum level, wherein the time interval is the duration of the ongoing rest period, determine a difference between a duration of the detected time interval and the minimum duration of the rest period for the patient, and control at least one output unit to output information representative of the determined difference and indicative of whether a rest period for the patient is ongoing.