8
●Regulations on fuel-burning systems specify a maximum
depression of 0.04 bar in such rooms.
●Hoodscanonlybeusedsafelywithappliancesconnectedtoa
chimneyiftheroomand/orflat(air/environmentcombination)is
ventilatedfromoutsideusingasuitableventilationholeapproxi-
mately500-600cm2 toavoidthepossibilityofadepressionbeing
createdduringoperationofthehood.
Ifyouhaveanydoubts,contacttherelevantcontrollingauthority
orbuildinginspector’soffice.
●Sincetheruleforroomswithfuelburningappliancesis“outlethole
ofthesamesizeastheventilationhole”,aholeof500-600cm2,
whichistosayalargerhole,couldreducetheperformanceofthe
extractorhood.
●Ifthehoodisusedinitsfilteringfunction,itwilloperatesimplyand
safelyintheaboveconditionswithouttheneedforanyofthe
aforementionedmeasures.
●Whenthehoodisusedinitsextractorfunction,thefollowingrules
mustbefollowedtoobtainoptimaloperation:
—shortandstraightoutlethose
—keepbendsinoutlethosetoaminimum
—neverinstallthehoseswithanacuteangle,theymust
alwaysfollowagentlecurveonly
—keepthehoseaslargeaspossible(120mmØmin.).
●Failuretoobservethesebasicruleswilldrasticallyreducethe
performance and increase the noise levels of the extractor
hood.
●Where flexible ducting is fitted the length should be no more
than:
— 3 metres with one 90° bend
— 2 metres with two 90° bends.
Bends of more than 90° will reduce the efficiency of the hood
and reduce the air flow.