Imagining that you are locked up in an enclosed space will make you upset and anxious. And, if his reaction continues at an extreme level one maybe suffering from Cleithrophobia.
Cleithrophobia is the fear of being locked up in an enclosed space. Those who have this fear the loss of freedom and movement that they need in order to feel healthy. This fear has a close association with Claustrophobia. The idea of being confined in an enclosed space that offers no way out can be upsetting in both Claustrophobic and Cleithrophobic. When they find themselves situated in this, they tend to have a panic attack which includes symptoms of nausea, dizziness, syncope and increase heart rate. People who have been kidnapped or held prisoner will be highly susceptible to this phobia. They will feel severe terror when faced with the idea of going through a similar experience at other times in their lives.
Seeking proper treatment from a qualified therapist can be of great help in dealing with the root cause of the fears. Conveying feelings and experiences with a trained professional can help in releasing anxiety and may embark progress. In some cases, panic treatments that offer solutions to coping with symptoms can assist to improve your quality of life.