smoke machines were popular in the 80's for highschool senior portraits, it
was, like, so cool.

I would imagine that the folks that sell the machine would have some
examples of its use.

In the links section of the z-prophoto mailing list (at yahoogroups.com)
there is a folder of places that sell studio specialty items like that.

dry ice is much more expensive and dissipates too quickly.

It's hard to get enough fog off of dry ice. It starts out well enough,
but the chunks of dry ice quickly start crusting over with water ice. I
tried using a portable gas cooker to keep the water heated, but the CO2
kept putting out the flame!  An electric hot plate might have done
better.

Small smoke machines are available and cheap around Halloween and they
work remarkably well. The model I have is called Fog Lite F/X. A quick
web search shows that it's available online for under $40.

This kind of smoke (technically it's actually a fog (droplets suspended
in air)) doesn't "hang", it just fills the room and reduces contrast.
Unless you use a "chiller".  I built the chiller on this website
http://www.virtualplacebo.com/halloween/fog.htm and it works great.  I
fill it with two bags of water ice and two pounds of busted up dry ice.
The smoke hangs near the floor and doesn't fill the room.

It's a gimmick, but it's fun. And on Halloween it spooks the heck out of
the kiddies.

Marc

I remember a photographer using a device which was intended to be used as a
smoker for putting liquid in which repels / kills insects.  It runs on
propane or something and you put the insect stuff in a little part and light
the fire and press a button to let the smoke out.

OF COURSE..... he did not use the bug killer stuff but used baby oil
instead.  It produced some nice white smoke!

~Adam N

Give consideration to risking your expensive camera in an environment
like this.  It sounds like a disaster waiting to happen for a digital
camera's CCD, but probably bad enough for a film type.  Be sure you
know what you're getting into here.