What is the glass air-wash system?

Question: What is the glass air-wash system, and where is it located?

Answer:  The glass air-wash system is a system that allows the stove to draw in clean room temperature air, to wash up the inside of the glass to help prevent excess soot buildup.  https://www.youtube.com/watch?v=4-yoLfydlhc

On the HP21, HP22 series, and HP61 models, the glass air-wash slider damper is located under the front opening, behind the front door.

On the HP50s model, the damper is the small tongue-like slider below the glass.