Welch ProBoost is an air cooled gas jet pump (commonly called a diffusion pump). The gas jet is formed by directing boiling silicone vapors through a hollow cone. There are no internal moving parts. The pumping action commences when the vacuum pressure in the still (i.e. wiped film) goes below 0.2 torr (200 millitorr). On an empty, leak free still, ProBoost backed by a rotary vane pump lowers the vacuum pressure to 0.00002 torr (20x lower in pressure than a 2-stage rotary vane vacuum pump can do alone).
ProBoost backed by a rotary vane vacuum pump will lower vacuum pressure to below 0.0001 torr in high vacuum and Schlenk lines. This high vacuum is invaluable to improve the results from reactions using air-sensitive compounds such as organometallics, metal amides, and hydrides.
ProBoost has a built-in control board for fan and heater. When you turn on ProBoost, the fan and heater both turn on. When you turn off ProBoost, the heater turns off immediately and the fan runs for another 20 minutes to cool the pump.