Hi Andy_con,
I would highly recommend you reveiw the Theses of John O'Hagan from the UK National Radiologocal Protection Board. The theses discusses risk analysis of doing laser shows. It is particularly good for audience scanning shows, but his principals of risk analysis are applicable for all show types:
http://www.pangolin.com/resguide09b.htm
If you plan on doing audience scanning, don't do it unless you have experience. Also, I would highly recommend you read my article on the subject:
http://www.pangolin.com/resguide09a.htm
Best regards,
William Benner