How do I inspect an old gas wall heater in a living room during the summer to insure it works properly?
I cannot answer your question but you may want to check if unvented heaters are lawful in that particular jurisdiction. Unvented flame heaters leave all of the products of combustion inside the home with the heat they produce. That exposes the occupants to CO, fuel gas fractions, and other combustion by products too numerous to name. There is a considerable body of medical evidence that those by products raise the likelihood of respiratory diseases in the home especially among young children. Some jurisdictions have banned unvented heaters for that reason.