A Peer Treatment Monitor's (PTM) presence is required to monitor your safety and assist you during your sessions. They should also be prepared to contact your guide for any non-emergency concerns and call emergency services if necessary, although this is highly uncommon.
During your first session, your guide will ask to speak directly with your PTM. If they cannot fulfill their responsibilities, your session will be postponed.
Guidance on finding and understanding the role of a PTM can be found here.