HP Jet Fusion 340 Product Documentation Site Preparation Manual page 54

Lamp duct recommendation
In order for the printer to function correctly, the lamp exhaust duct should create no more than 125 Pascals of
back-pressure at 3680 liters per minute (0.5 inches of water at 130 ft³/min) of air flow. In order to achieve this
with a passive exhaust duct:
A duct of at least 10 cm (4 in) is required
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Remove the silencing foam from the duct before connecting any external ducting.
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Avoid sharp bends in the duct, and use no more than three bends of minimum radius 20 cm (8 in).
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For a duct longer than 3 m (10 ft), the diameter of the duct should be increased, or use no more than two
bends up to 6 m (20 ft) in radius.
50 Appendix B Ducts and HVAC recommendation ENWW