Check for smoke alarms. The fog machines will set them off just like a real fire. You will need to disable the smoke alarms while you use the fog machine.
don’t leave your fog juice in the fog machine. If left in the heat it will turn it into a sludge and you will need to buy a new fog machine.
Don’t make people stay in the fog for too long. It can cause them to cough.
Ask before you give them the business. Preferably at the start of the event and before the fog if you have crew that you are unsure of.
Block the windows so that the fog doesn’t escape.
Lighting
If you plan to use a strobe light in the fog, make sure you announce that warning cause smoke amplifies light. Epilepsy and Migraines
Small fog machines
the small fog machines use a different juice.
small fog machines can be good for “close magic”