What is the benefit of indirect waste at a culinary sink?

The main benefit of using an indirect waste at a culinary sink is to prevent harmful gases and unpleasant odours from entering your home. While using the sink, gases, like sewer gas that may be present in the drainage piping can be pushed back up by water or air pressure.

An indirect waste provides an air gap which breaks the direct connection or channel that would otherwise allow gases to travel from the drainpipes into the room where the sink exists. This air gap can be built into the fixture or can come as its own separate add-on component to connect your P-trap assembly to the garbage disposal drainpipe.