Recently have been researching carbon monoxide and detectors to find that most only go off at 30ppm for fifteen minutes or so but don't cover if there is momentary backdraft bringing co into the house for less time. So my question would be how incomplete is the combustion on most water heaters if it's just maintaining the temperature and or the likely scenario where the hot water is depleted and the flame loses heat and in theory produces more co. I hear story's of water heaters back drafting from home inspectors but the alarm never goes off and also how dangerous even small levels of co are overtime with lasting effects even after being removed from the home/building. Curious to know what you all have learned from your experience in the field.