"Volunteers"

I have just purchased a coffee from the outpatient cafe ? A volunteer suggested to the staff member that they have a party, dance naked on the tables and take white stuff. When I asked if they were a volunteer the staff member said yes, then the volunteer suggested that I take photographs of them partying naked. How on earth can a parson such as this be allowed to volunteer in a hospital where confidentiality , dignity and respect let alone the Caldicott principles,should be adhered to? What are the procedures fir vetting and barring volunteers? Who supervises them? Who is accountable? What do you propose to do about this short and long term?