17
Preferred 4” Hoods
When you have a 4” (10cm) Hood
Maximum length of 4” diameter metal duct.
Number of 90˚
elbows/bends
Rigid
Thick Wall Flexible Metal
(fully extended)
0
64ft
19.5m
8ft
2.4m
1
54ft
16.5m
8ft
2.4m
2
44ft
13.4m
8ft
2.4m
3
35ft
10.6m
8ft
2.4m
4
27ft
8.2m
8ft
2.4m
Acceptable 2 ½”Hood
When you have a 2 ½” (6cm) Hood
Maximum length of 4” diameter metal duct.
Number of 90˚
elbows/bends
Rigid
Thick Wall Flexible Metal
(fully extended)
0
58ft
17.6m
8ft
2.4m
1
48ft
14.6m
8ft
2.4m
2
38ft
11.5m
8ft
2.4m
3
29ft
8.8m
8ft
2.4m
4
21ft
6.4m
8ft
2.4m
For exhaust systems not covered by the exhaust duct length charts (such as multiple unit hook-ups,
plenums, and power-assist fans), call our Customer Care Center:
TOLL FREE 1.888.9.FNP.USA (1.888.936.7872).
Maximum Length of Exhaust Duct