The fan in a Local exhaust ventilation (LEV) systems creates a pressure differential, as air is sucked or blown into the duct.

The volume of air that travels through an LEV system depends on the air velocity and the size of the air duct. To calculate this airflow is to determine how efficiently the system is working and whether you need to replace any components.

Duct DiameterOpen AreaCircumferenceAir Volume m3/hr
inchesmmm2mm1516171819202122
1.6400.001312668727781869095100
2.0500.0020157106113120127134141148156
2.4600.0028188153163173183193204214224
2.5630.0031198168180191202213224236247
2.8700.0038220208222236249263277291305
3.1800.0050251271290308326344362380398
3.91000.0079314424452481509537565594622
4.71200.0113377611651692733774814855896
4.91250.0123393663707751795839884928972
5.51400.01544408318879429981053110811641219
5.91500.01774719541018108111451209127213361400
6.31600.020150310861158123013031375144815201592
6.91750.024155012991385147215591645173218181905
7.11800.025456513741466155716491741183219242015
7.92000.031462816961810192320362149226223752488
8.92250.039870721472290243325762720286330063149
9.82500.049178526512827300431813358353437113888
10.82750.059486432073421363538494063427644904704
11.02800.061688033253547376839904212443346554877
11.83000.070794238174072432645804835508953445598
12.43150.077999042084489476950505330561158926172
13.83500.096211051955542588862346581692772747620
14.03550.0990111553455701605864146770712774837839
15.74000.1257125767867238769181438595904895009953
17.74500.159014148588916197331030610879114511202412596
19.75000.196315711060311310120171272313430141371484415551
21.75500.237617281282913685145401539516251171061796118817
22.05600.246317591330014187150741596016847177341862019507
23.66000.282718851526816286173041832219340203582137522393
24.86300.311719791683317955197082020021322224442356624689
28.07100.395922312138022805242302565627081285062993131357
31.58000.502725132714328953307623257234382361913800139810
35.49000.636228273435336644389344122443514458044809550385
39.410000.7854314242412452394806650894537215665495937662204
44.111200.985235195320156748602946384167388709357448178028
49.212501.227239276626870686751047952283939883579277597193
56.014221.58814467857609147797194102912108629114346120063125781
59.115001.7671471295426101788108149114511120873127235133596139958
63.016002.01065027108573115812123050130288137526144765152003159241
78.720003.14166283169646180956192265203575214885226195237504248814