Yes... honestly it's a glaring design flaw in all these diesel heaters. IF the exhaust clogs up.... it's still burning stuff, and it has heat, so hte heat builds up and causes the gaskets to fail INTERNALLY in the unit. Then the exhaust can start coming out the heat output port. Kind of blows my mind that these are produced the way they are, the failure mode can literally kill people. I see stories of people dying occasionally because of these, and now I always wonder if it was an improper installation, or if it was so cold that the exhaust clogged and the interior filled with CO. I actually do have a generator, brand new, but it's still in the box. Was trying really hard to not use it.
The gas furnace in my basement is mounted horizontally. It has a forced fan for exhaust and a pressure sensor with about 4" diameter foil membrane, which detects slight vacuum. Then furnace is allowed to light. There is a glowing bar ignitor and a (rectification?) flame sensor checks that it is burning, if not shuts off, waits, retries. There are several over-temperature sensors which would open if flame backed up or cooling air (air handler) was blocked.
All that ensures there isn't combustion without ventillation. Now if exhaust pipe was damaged, it wouldn't know about that. Due to some sheetrock repair in the vicinity of flue that I didn't get to observe/inspect, I bought a CO alarm. Only time it ever went off was when I left oven on overnight. We have since learned that although these alarms have display with 1 ppm resolution, they are programmed for "don't ask, don't tell" below about 30 ppm. HVAC techs buy an expensive wearable alarm that is programmed to tell them what they're exposed to.
Cheap passive burners have no safety features. Designed for where life is cheap.
I tested my unit with a CO detector when I received it placing it directly in the path of the exhaust for over a minute several times to see if I was doing something incorrectly. It never triggered. Diesel combustion produces less CO than regular gas fuel. So it is my guess you would require a much more confined space and a longer duration to suffer any effects of a “leak”. Which is a different animal to sleeping with an operating Buddy heater, or feeding exhaust directly into your confined sleeping space.
Sufficient O2 and well adjusted flame, low CO production.
Operated in a closed space so O2 levels drop, then it will make CO. Or a badly operating unit.
Old cars ran with excess fuel to avoid detonation, and that makes CO. Closed-loop fuel injection, runs 0 to 1 ppm.
Safety gear and alarms do nothing when everything works correctly, could save a life when there is a problem.