Operating a gas clothes dryer without venting is not safe and could lead to carbon monoxide poisoning or an explosion. Ventless dryers are not available as gas appliances. The gas trapped in the room containing the dryer has no place to disperse if not properly vented.
There is a reason one cannot purchase a gas dryer without a vent. Operating a gas appliance without venting, especially in a small space, is dangerous. One danger is that of carbon monoxide poisoning from the trapped gas fumes. This is especially dangerous in a small, well-insulated space that is more airtight. The dryer exhaust must be vented outdoors rather than to an attic or another space inside the structure.
Carbon monoxide is difficult to detect and causes illness, brain damage and death. Disorientation, nausea and headache are easily blamed on other factors.
Another risk of improperly vented gas dryers is fire or explosion from heated gas fumes. Dryers are a cause of many fire-related deaths each year, and this is increased with improper venting. It is also not acceptable to vent the dryer into a container of water rather than vent outdoors. With proper venting, it is necessary to clean exhaust systems to make sure there is no blockage.