Glossary · Testing & air leaks
Draft (chimney draft)
Also called: flue draft · draft test · draft pressure
The upward pull in a chimney or vent that carries exhaust out of the house; weak or reversed draft lets combustion gases spill indoors.
What it means
Hot exhaust rises, creating a slight suction in the chimney that draws gases up and out. Auditors check draft with a pressure gauge or by holding a smoke pencil at the appliance's draft hood to see whether smoke is pulled in. Draft is weakest when the chimney is cold, blocked or oversized, or when the house is depressurized.
Why it matters in an audit
Poor draft can lead to backdrafting and carbon monoxide in the house, so it's checked during every combustion safety test.