In the United States, all gas dryers must be vented to the outdoors by law!
The path of the dryer duct:
Any lint that escapes the dryer's lint filter should be blown right outdoors. (Any accumulation which occurs in a dryer's ducting is usually a sign of poor air flow, especially at the location(s) it occurs.) In such cases, the vent line should be evaluated to locate and correct any deficiencies it may have.
The vent should be as short and as straight and with as few elbows as possible. The more bends and turns, the greater the reduction in air flow there is, and the more areas where lint can accumulate. More bends will also hamper dryer vent cleaning, which should be performed yearly, if not seasonally.
It is sometimes possible to tell if a dryer's vent is the cause of poor drying by totally removing the vent line from the dryer and doing a couple of loads. If drying improves, you can be sure the vent is (at least part of) the problem.
When attaching multiple sections of vent pipe together, Dryer Vent Wizard does not use sheet metal screws. We use metal foil tape instead. Any protuberances into the vent will cause obstructions where lint can accumulate --eventually leading to a restriction, which will hamper dryer vent cleaning and allow lint to build up. Those protuberances will also make the inevitable dryer vent cleaning much more difficult.