For as many CO alarms we go to that are false (alarms) because the owner does not know they need to change battery’s, clean the unit or replace it every 7 years, we do come across a few that are legitimate. It is amazing how deadly CO can be. This evening was the third incident for me in last 6 months where a properly function CO alarm saved a life or two. Tonight’s call pointed to a faulty furnace pushing out nearly 10,000 PPM of deadly CO (we go on air at 35ppm). It is pretty simple, if the couple did not have an alarm or worse yet, had one with dead batteries they too would likely be dead by tomorrow morning.