Technical Standards and Safety Authority (TSSA) G3 Practice Exam

What is the minimum vent height for a roof with a 12/12 pitch serving a natural gas fired appliance?

1. 2 feet

2. 4 feet

3. 6 feet

4. 10 feet

The correct answer is: 4 feet

The minimum vent height for a roof with a 12/12 pitch serving a natural gas-fired appliance is determined by safety regulations to ensure proper venting and ventilation of exhaust gases. A vent height of 4 feet is necessary to create adequate clearance above the roofline, allowing for the dispersion of combustion products and minimizing the risk of backdrafts or re-entry of exhaust gases into the living space. According to safety standards, a vertical vent must extend far enough above the ridge of the roof to ensure effective operation. The 4 feet height is typically specified for roofs with steeper pitches, like a 12/12 pitch, as it helps to mitigate the effects of any potential wind conditions that could adversely affect the venting performance. Choosing a lower vent height would not provide sufficient clearance for effective venting, while selecting a higher height may be unnecessary and could complicate installation or maintenance. Therefore, 4 feet strikes an appropriate balance between safety and practicality in this context.