Common Roots blower sealing form of packing gland type, rising ring type, labyrinth type mechanical seal, etc. What form should be used, mainly according to the nature of the gas (whether it is poisonous, can be expensive, etc.) and determine.
When pressurizing gases such as air, a pair of gland seals are often configured between each bearing and the cylinder - a total of four such seals, and a set of oil seals is provided at the outward end of the shaft.

In the pressure sending oxygen, nitrogen, sulfur dioxide and other lubricants (grease) can not touch the gas, in the cylinder through the part, set up four groups of mechanical seals, so that the bearings, gears, wheel sliding part of the complete isolation of the gas, this configuration is the rotor bearing span increase.
In the case of gas and methane, the bearing box is often closed, and a set of gland seals is used in the through part of the shaft. Mechanical seals can only be used if hydrogen is being pressurized.