Which type of vent is used by a gas-fired toilet?

The use of a single wall vent is appropriate for a gas-fired toilet because this type of appliance typically operates at standard temperatures that do not require the extra insulation provided by a double wall vent. Single wall vents are generally sufficient for venting the combustion gases produced by gas appliances, as long as they are correctly installed and maintained according to local codes and regulations.

In the context of gas-fired toilets, which are not high-efficiency appliances, the venting requirements are less stringent. The single wall vent effectively allows for the safe expulsion of gases without the risk of overheating or fire that would necessitate a double wall or other vent types which are used for applications that generate higher temperatures or require additional safety measures.

Therefore, the single wall vent option is suitable and compliant for gas-fired toilets given the operating parameters and safety regulations applicable to such fixtures.