You can buy cheap "smoke/fog machines" which give a similar effect with better controls as the "fog" is water based, much the same as used by mobile disco's.

It seems a great idea until some halfwit decides it's funny to put it in his mouth when they've had a few drinks.

Be careful you do not create a confined space

The thing I suggested, I have seen similar in garden centres. You have a small metal stand about desk height with a glass bowl on top, designed to be indoors. This produces just enough mist to fill the top of the dish so it overflows to the floor. The mist seems heavier than air as it drops to the floor and is not particularly capable of filling a room as far as I could tell. I guess if you had a cupboard you might. So very unlikely to get anywhere near the smoke detectors. I suspect it has an off switch.

You can use them in ponds too. No heat involved, it is not steam just vapour made from water.

I guess as we are on a negative vibe, don't forget to ensure your fog machine is Inspected / PAT. Don't forget to cater for diabetics and others with food intolerance. First aider in case of fainting in fright.....

Have a nice party, what a nice thing to do for your employees.

Chris