Gas dryers cannot be vented indoors because of the emission of by-products produced during the drying process. During the combustion that takes place when a dryer is fueled by natural gas, water vapor and carbon dioxide are released. These must be vented outside.
All indoor dryer vent kits indicate explicitly that they are not to be used with gas dryers. The safety of venting any dryer indoors is questionable, as excess moisture can accumulate and cause problems in a home.
It is important to have a qualified technician perform the installation of a gas dryer. While an electric dryer can simply be plugged in, there are more hazards when dealing with a gas appliance.