Pulse-Bac HD - The Pulse-Bac HD (Heavy Duty) vacuum is a 20-gallon, continuous-duty unit offering 270 CFM at 80" wg. The unit features a unique internal filter arrangement of 3, 10" long, spun bond polyester cartridges that are 95% efficient to 0.1 micron. The unit's patented filtration system pulses one of the three filters every five seconds in rotation to ensure continuous operation in demanding environments like concrete and drywall dust collection. Pulse-Bac vacuums also feature a highly stable 5-caster base that can support up to 300 pounds. The Heavy Duty Pulse-Bac is ideal for floor surfacing operations that generate dense dust and it can is also work in certain source capture applications for grinding stations. Please note that an extension fitting is available to adapt the Pulse-bac vacuum head to 40 and 55-gallon drums.