The small button, usually located underneath the control panel on the steam shower range is not actually a button at all. For reference see the picture below.
This is your thermostatic probe, which reads the temperature within the cabin. When steaming you set a desired time and temperature, sit back, and relax. The thermostatic probe will make the steam generator automatically stop producing steam when the set temperature is reached, much like a central heating system. When the cabin drops a few degrees, the probe will communicate this to the generator and activate the steam again. You can reactivate the steam by manually increasing the desired temperature via the control panel. To learn how to do this please refer to our Control Panel Video Playlist