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Really strange device mounted into the flue of a boiler I tested yesterday
The holes are designed to create turbulence. A thermostatically activated fan on the back (not pictured) blows air through the holes to recover flue pipe heat into the conditioned space. One small problem is the desirability of having flue gases exit the building. Flue gases on this thing spilled like crazy from the boiler into the living space probably because of this device. I'm always struck by just how infrequent carbon monoxide poisoning seems to be. If you were deliberately designing an something with the express intent of inducing carbon monoxide it would probably look like this. Or a generator perched in a garage.