There are professional standards. Show lasers are very definitely NOT harmless. I have mild but permanent retina burns from a home-made 40mW projector I put together in the 2000s.
Modern show lasers are more likely to be around 1W for smaller events, around 20W for stadiums and up to 100W for the biggest outdoor events. Getting the beam from any of those in your eye will blind you almost instantly.
So audience scanning is carefully calibrated. The lasers are set up either to scan balconies and ceilings, to move at a certain velocity to minimise dwell time, to lose most of their brightness below a certain height - or all of the above.
Professional shows require a "variance" - basically regulation and associated paperwork - to make sure no one is hurt.
Of course any idiot can buy a 1W show laser for less than $1k now, but the US has quite strict legal requirements for public use, and anyone who causes serious eye damage is potentially on the hook for a law suit and bankruptcy.
Modern show lasers are more likely to be around 1W for smaller events, around 20W for stadiums and up to 100W for the biggest outdoor events. Getting the beam from any of those in your eye will blind you almost instantly.
So audience scanning is carefully calibrated. The lasers are set up either to scan balconies and ceilings, to move at a certain velocity to minimise dwell time, to lose most of their brightness below a certain height - or all of the above.
Professional shows require a "variance" - basically regulation and associated paperwork - to make sure no one is hurt.
Of course any idiot can buy a 1W show laser for less than $1k now, but the US has quite strict legal requirements for public use, and anyone who causes serious eye damage is potentially on the hook for a law suit and bankruptcy.