Draft
The pressure difference that draws in combustion air and vents flue gases from a gas appliance to the outside, a condition for safe and efficient combustion.
What is draft?
Draft is the pressure difference that sets the gases around a gas appliance in motion: it draws in the air needed for combustion and pushes the resulting flue gases to the outside through the vent. Without sufficient draft, the appliance cannot operate properly.
Natural draft and forced draft
Natural draft relies on the density difference between hot flue gases and ambient air, while forced draft uses a fan to ensure venting. The choice depends on the type of equipment, the gas burner and the building’s configuration.
Why is draft a safety matter?
Insufficient or reversed draft can push flue gases back into the room. Because these gases contain carbon monoxide, any draft fault must be taken seriously and diagnosed by a qualified technician. Checking draft is part of the verifications during commissioning and maintenance carried out in line with applicable requirements.