[np-]

Ventless driers typically use a condenser to pull out the humidity, condense it into water, and drain it into the same drain your washer uses. If it's working correctly, the humidity shouldn't be going into the air.

[r2_pilot]

Cool, I learned something. But it also does seem like that would take additional energy(due to the particularly high enthalpy of water, if I remember my concepts correctly) so at least where I am, venting the excess moisture is the most expedient method.

[ygra]

Venting the moisture also vents the heat. A modern dryer uses a heat pump for both heating the air and pulling the water out of the air. Although I guess with lifetimes of the devices and the relative cost of power (or gas even) between NA and EU they might be much more common around here. With an insulated house you also don't really want to have too many holes in the building, especially not ones intended to remove heat.

[ta1243]

Or indeed into a container which you then empty