Final answer:
The Technical Standards and Safety Authority (TSSA) is responsible for administering regulations for the installation and service of gas appliances in Ontario.
Step-by-step explanation:
The organization responsible for administering regulations for the installation and service of gas appliances in Ontario is the TSSA (Technical Standards and Safety Authority). TSSA is a non-profit organization that is mandated by the provincial government to ensure public safety in areas such as fuels, boilers, and pressure vessels. They oversee the licensing and certification of technicians and inspectors, as well as the enforcement of regulations related to gas appliances.