Vacuum excavation is the process of digging with either the suction power of a positive displacement (PD) blower or moving materials with the high-powered air conveyance of a fan system.
Effective PD blowers operate above 25” Hg (inches of mercury) and must be used in conjunction with pressurized water to break up materials and create a liquid slurry to be vacuumed up.
Fan systems are typically rated between 1,000 and 5,000 CFM and aren’t very effective for excavation purposes. True suction excavators and air conveyance systems used for excavation will operate at 20,000 CFM or higher and move materials at exceedingly high throughput rates.