The US4000 Dual Motor Air Duct Cleaning System offers high performance in a compact, lightweight design. These vacuums incorporate twobackward incline motor and blower assemblies, which create a powerful combination of vacuum and air flow. Each system incorporates an exclusive 3-stage filtration system which includes final stage H.E.P.A. (High Efficiency Particulate Air) filter rated at 99.97% @ 0.3 micron particles and larger, DOP tested. This actually meets or exceeds OSHA, EPA and NADCA standards for cleaning the air of toxic and nuisance dust.