Newer designs require that the flame be adequately shielded to prevent possible ignition of spilled flammables in the area. Ours has some sort of thick aluminum element on the bottom of the heater which allows air to pass for burner use but will arrest a flame. This element is very much a dust filter as well and gets clogged. Clogging causes problems with the burner flame which can result in triggering a fuse device in the thermocouple rendering it non-functional. Initially, the manufacturer wouldn't honor warranty repairs as these elements had a maintenance requirement. They needed to be kept clean and free of dust. Since they aren't removable and sit about 2" off the floor under the heater, there's no real way to access them without some sort of custom vacuum attachment. There's also no way to visually inspect them to see if they are getting clogged. No where on the heater is there a sign mentioning the flame arrestor or noting it's location. What little old lady or man is going to be able to deal with this dumb device? Our thermocouple was failing about every 8-9 months even though I was trying my best to keep dust out of the flame arrestor. I can't imagine some old lady or man doing this but having to call for service every year at the cost of a couple hundred dollars or so to clean it and replace the dead thermocouple.
Eventually, some class action suit was filed and the manufacturer had to find a way to resolve the issue. By then, the manufacturer had come up with a thermocouple with a reset switch. I had to pay shipping only and was able to install it myself. Still, that doesn't fix the clogging of that stupid flame arrestor. My rant.
You have to love Dilbert:
I wonder if there really are companies that create bizarre maintenance requirements just so customers can never claim warranty service.
I've seen tech support discussions that include unreasonable requests which I guess is a related phenomenon.