What does the term "draft" refer to in gas systems?

The term "draft" in gas systems refers to a pressure difference that causes air or combustion gases to flow. This pressure difference is crucial for the proper operation of gas appliances, as it helps to ensure that combustion gases are effectively vented outside, preventing backdrafts and ensuring safety.

A draft can occur due to various factors, such as the buoyancy of hot gases rising through a flue, creating a lower pressure at the base of the chimney or vent. This differential pressure helps to draw fresh air into the combustion zone and expel exhaust gases, maintaining the efficiency and safety of the gas system.

Understanding the workings of draft is essential in ensuring that gas appliances function correctly and that there is adequate ventilation to prevent the buildup of harmful gases indoors.