For example - our household has forced hot water heating through pipes to radiators in each room. However - there is a "boiler" which heats that water - it run

For example - our household has forced hot water heating through pipes to radiators in each room. However - there is a "boiler" which heats that water - it runs on natural gas. When we moved in, I installed some air quality sensors - and noticed high levels of carbon monoxide - I was concerned, and searched and searched - and finally found that at some point, a service technician must have needed to do some testing on the output exhaust levels, so they drilled a hole in the pipe that carries that to the exterior... It had been leaking for years before we purchased the home...