A facial sauna system has an electric heating element at the bottom of it.
It heats the water (which is held in a small reservoir) to the boiling point, causing the steam to rise.
The small size of the reservoir means you can expect quick steam production.
An ergonomically designed mask is placed over the reservoir to capture and funnel the steam to your face. You can control the amount of steam that your face is exposed to by the distance of the mask to your face.
Bringing your face into direct contact with the mask will give you maximum deep cleaning action, but you should only hold this position for a few moments at a time unless you have high tolerance for the heat.
If needed, you can try raising your head every few minutes or so for a breath of cooler air.
Benefits
Two facial sauna benefits include deep skin cleansing (by rinsing out your pores) and unclogging stuffed sinuses.
Steaming your face helps clean out your pores from deep within - much deeper than merely washing dirt off the surface.
Also, anyone with a simple cold or a more serious condition like bronchitis, sinusitis, asthma and hay fever can use a facial system as an inhaler or vaporizer.
Some people report having success using them for acne treatment as well.
For step-by-step instructions on creating your own spa-like facial at home, read Spa Style Facial.
Operating Tips
Most facial saunas have a very small reservoir so the water can heat up fast. The downside of this is that the water evaporates quickly, so if you want to use it for a long session, you might want to keep a tall glass of water nearby. That way, you can quickly refill the reservoir when/if it goes dry.
Unfortunately, the small reservoir also means that the facial unit can't be used as an overnight vaporizer. If your sinuses are keeping you awake at night, you would be better off with a traditional vaporizer that provides steam for several hours.
Steam is great for deep cleaning your skin, but you can also add "extras" like essential oils to the water to enhance the whole experience. Just a few drops is all that's needed. (I do recommend doing some reading about essential oils first if you haven't used them before).
Want to give it a try? The Steam Facial By Kaz is inexpensive and has some pretty good reviews.