In the sophisticated setting of artificially ventilated persons at home errors or miscues can be lethally for the patients. Therefore, the joint research project ‘MeSiB’ aims at implementing an Ambient Sensor System (ASS) that detects, among other things, care procedures and the state of the patients. Within MeSiB, these sensor values are further examined in a so-called ‘SafetyBox’. If a critical situation is detected, an alarm will be generated and sent to an emergency alert or telemedicine station. This work focuses on the requirements for the ASS. Therefore, two different scenarios are presented. Furthermore, the process of the requirement extraction is described. The results of this work are comprised of the functional and the non-functional requirements for the ASS.