In this application, as the ambient temperature within the greenhouse increases, the wax melts, activating the plunger and opening the vents.

When in the kiln, the wax melts off and the carbon, that results from oxygen reduction, replaces the wax.

As the candle burns, the wax melts and the follower holds the melted wax in, whilst the stricture rests on the topmost solid portion of wax.