It is not smoke. It is mechanical pump oil vapor. It is normal for the pump to emit vapor when pumping on a chamber from atmosphere. Since all the air that is removed from the chamber by the pump moves through the oil in the oil resevoir, some of that oil is vaporized when a lot of air is moving through it. When the pressure in the chamber is reduced to a few hundred torr, the oil vapor or "mist" should reduce dramatically. It is recommended to intall an oil mist eliminator on the exhaust of your mechanical pump to reduce it even further.
Category: Vacuum Systems
Sub-Category: Oil-Sealed Mechanical Vacuum Pumps