Fume extraction hoods and cabinets benchvent bv660h d the benchvent techflo fume cabinet bv66oh d is a fume filtration hood of 355msup3hr air volume capacity intended for use where external venting is required the attached flexi duct vents to atmosphere either through a standard domestic vent or a convenient window filtration is carried out by a 3 stage graduated fibre filter with a high dust holding capacity that ensures a long filter life this dual process of filtration and extr