What is the minimum height above the peak for a masonry chimney when used for a gas appliance?

The correct answer regarding the minimum height above the peak for a masonry chimney used with gas appliances is 2 feet. This minimum height is established to ensure that the chimney effectively vents combustion gases away from the building and prevents them from re-entering.

When a chimney is too low relative to the peak of the roof, it can cause improper drafting. This improper draft can lead to the buildup of harmful gases like carbon monoxide inside the living space or insufficient venting, which can reduce the appliance's efficiency.

The regulation for a minimum height of 2 feet ensures that the chimney rises above the roofline sufficiently to allow for an effective escape of gases, especially in varying wind conditions. This height requirement is part of safety codes and building regulations designed to mitigate risks associated with gas appliances.

While the other options present various heights, they do not meet the established safety standards necessary for proper and safe operation of gas appliances vented through masonry chimneys. Proper venting is essential for the safety of the structure and its occupants.