These inexpensive smoke or fog machines can open up a few different projects to entertain the kids and you will find a few posts here:
They are also a must for any Halloween setup. Look out for a post on how to make a low lying mist as this is a project I want to do this year.
They come in a variety of sizes all determined by the heating power (wattage) of the unit.
To work they heat up a mixture of water and glycol that produces a vapor. This is then forced out of a nozzle where the warm, vapor mixes with the cooler air to form fog.
The machines take some time to get to temperature but once at temperature they usually only deliver a few 10’s of seconds of smoke before having to heat up again but this is more than enough for most situations.
The higher the wattage the larger the amount of fluid they can heat and thus more smoke / fog. We have had a number over the years from 400 to 700 Watts and all have proven to provide a more than adequate amount of smoke for our needs.
Smoke Machine Maintenance
We have had a number of machines as you have to be careful to make sure you clean them properly after every use otherwise the small nozzle gets blocked. We also use them fairly heavily and on one a pump eventually broke.
See the post on smoke machine maintenance before you consider buying a unit.
Another good post on smoke machine maintenance can be found at wikiHow
Smoke Machine Fluid
There are many makes of fluid but I find making my own to be the best option – Home made smoke machine fluid