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 36ft 10.9m
1 54ft 16.5m 31ft 9.4m
2 44ft 13.4m 27ft 8.2m
3 35ft 10.6m 25ft 7.6m
4 27ft 8.2m 23ft 7.0m
Acceptable 2 ”Hood
When you have a 2 ” (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 28ft 8.5m
1 48ft 14.6m 23ft 7.0m
2 38ft 11.5m 19ft 5.7m
3 29ft 8.8m 17ft 5.1m
4 21ft 6.4m 15ft 4.5m
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 888 9FNP USA
(888 936 7872).
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