I suppose there are positives and negatives. Also depends where you are, what's happening. My positive would be that nothing beats the "real thing" - or as close as you can get. Negatives would be heart attacks, injuries, someone calls the fire brigade, press, interuption to service and recuperation time. I have done something similar to what I think you are proposing, where I stated at the end of the event, that in 5 minutes time we are going to test our evacuation plan, and we would appreciate as many participating as possible - if you don't want to be involved please leave now, as you have 5 minutes.

My view has always been that if you what an accurate and effective test of your evacuation procedure you shouldn't really tell anyone prior to the test. If certain people are aware, or certain people are excluded you wont get a true picture on how effective your procedures are.

I would suggest that only those who need to understand what to do in a fire evacuation need take part in a routine drill. That would include staff, long term contractors and in the case of student halls of residence, the students. All of this group would have been issues with instructions of what to do so have an active part during an emergency. The drill tests their knowledge of that plan. People that should not participate are those who have a more passive role in that they are not required to know the emergency plan and will be guided out by staff. This would include shoppers, hotel guests and hospital patients.