Physical restraints negatively impact the physical, mental, and social well-being of patients. However, elderly people with dementia are often physically restrained by preventing nasogastric tube (NG tube) self-removal. This study aimed to examine alarm threshold settings limited to the actions that the subject makes contact with the NG tube out of feeling uneasy for the NG tube (assumed self-removal actions) using a contact sensor system in order to achieve non-physical restraint. In this study, subjects with experience in caring for older people with dementia were required to perform an assumed self-removal action along with 15 kinds of non-self-removal actions, while we observed the contact detection and measured the voltage. The alarm thresholds for the assumed self-removal action were examined from the ROC curve using the voltage zero time and the number of times the voltage was up and down during each action as a variable. The system presented in this study allowed us to reduce the false alarm rate from 23.3% to 8.5%. Furthermore, we used this alarm threshold to verify the data of three new subjects, observing a false alarm rate of 0.0%. Our future research would focus on investigating and evaluating elderly with dementia using the alarm threshold of the assumed self-removal action that we examined. In addition, we would use ICT to link contact detection with the nurse call system. Clinical Relevance- In this study, we examined the alarm threshold limited to the expected self-removal action using a contact sensor system. We showed that it is possible to detect the NG tube self-removal with few false alarms.