Xpelair Simply Silent Instrucciones De Instalación página 7

FIGURE 5 - Ducting DOs and DON'Ts
GOOD – Any condensation build-up will run towards external vent.
BAD – Any condensation build-up will run back into the room.
BAD – Any condensation will be trapped, causing collected water to
stagnate, constrict or even block the air flow through the duct.