Typically a Roots type rotary lobed blower. These pumps act as high capacity “boosters” to mechanical backing pumps at specific vacuum ranges. There are also some vapor pumps that are referred to as booster pumps.
A pump with less than 500 gallons per minute rating; usually an auxiliary to other pumps on fire apparatus. Used to supply water through booster hose. Fire pump used to boost the pressure of the existing water supply within a fixed fire protection system.