Can a Dryer Vent Be Indoors?
No. Dryer vents absolutely have to run outside. They might travel through a tube to get there, but they have to vent their air to an exterior area. Dryers expel chemicals that can be dangerous to breathe.
Even electric dryers pose health risks if they're not vented outdoors, but exterior venting is especially important with gas dryers, which can emit carbon dioxide, a potentially deadly gas.
For each load of clothes you dry, a gallon of water is released into the air. If the humidity level of your home is already high, adding this much water vapor from indoor venting would not be a good idea. Consider, also, the mold and mildew that can grow from condensed water vapor.
A dryer vented to the outside allows lint to exhaust into the outdoor air, rather than remain trapped in your lint screen. Inside venting can also exhaust lint throughout your house. Worse is the risk of tiny fibrous lint particles being breathed into the lungs of family members and visitors.