What defines a direct vent system?

A direct vent system is primarily defined by its method of drawing air for combustion and expelling exhaust. In such a system, all necessary combustion air is sourced from outside, which prevents the system from depleting indoor air quality. This configuration also enhances safety by ensuring that any potential hazardous gases produced during combustion are vented directly outside, away from living spaces.

The distinction is important: while some systems may utilize indoor air for combustion, a direct vent system explicitly maximizes external air, ensuring that the combustion process is not reliant on the air available inside the home. This allows for improved efficiency and helps maintain stable atmospheric conditions inside, as the indoor environment is not affected by the combustion process.