Earlier quoted context omitted.
There are other methods to prevent such occurrences: furnaces have "flame out of bounds" sensors and/or chimney flow sensors: this is very good at preventing the furnace from starting a fire of its own. If there's already a fire present, whether furnace decides to stop operating or not is usually irrelevant (you can get a gas leak from a damaged furnace even if it's off). I do not see why _remote_ control should be a…
So, circumvent your furnace control logic to burn at max rate when it receives no commands from it remote controller, then go somewhere for a week. Engineers are stupid people, you know.
So, in this case, "burn at max rate" _is_ the safe setting to be used when the controller dies. The only unsafe situation that it will cause is that the hot utility water will be scaldingly hot, but there will be no increased danger of fire nor of CO poisoning.