H-P Products. The Element central vacuum system’s dual-filtration design incorporates a first-stage cyclonic action to separate most dust and dirt from the air column, followed by a permanent, two-stage filter that never needs replacement to segregate fine dust particles. The manufacturer says the unit does not require outside venting, but provides an optional vent kit. Models range from 520 to 575 air watts of power with 64.7 to 66.7 decibels of noise. A translucent 6-gallon bucket requires emptying three to four times per year. 800.822.8356. www.elementvac.com.