Fog machine for first dance - worth it?

If its going to be a small mist of fog i think it would be fine. It will be seen in photos. i wouldn't necessarily pay extra for it - what if it blows out too much and you guys start coughing? or your guests do and then it ruins the moment? I'm a little skeptical of them but if its something you very much want then i would talk to them and make sure they don't go over board

Actually, these are amazing. Lots of inaccurate info here in this thread so let me help out. We thought it was great for our photos and you will too. We checked it out a lot before we went and did it ourselves. Here's what I found out:

First, the picture above showed and what you're looking for is a low-level fog, most often created by dry ice. When dry ice evaporates it transitions into a fog right before it becomes a colorless odorless gas - CO2 the same gas be breath out. Think Halloween punch bowls.

This type of fog will not cause your guests any breathing problems, won't deposit 5 gallons of water on a floor - it's CO2, not H2O, and will not cause mildew, or spread legionnaires disease. Unfortunately, it also will not cure cancer. But it does make really cool photos like the one above and as you can see for yourself, clearly not tacky, not 80's, 90's but a super romantic look - when we look at our photos we feel like we were just lost together dancing on a cloud.

It works best in rooms that do not have an aggressive active airconditioning system that is creating huge air currents and in environments that are not really warm/hot - so not ideal in spaces with lots of air circulation or outdoors, and not in a venue during summer that is oppressively hot, which luckily was not an issue for us. However, the effect is very quick, awesome for photographs effect, but will not hang around much longer than halfway through your first dance - we would have loved it to be there for everyone to enjoy too.