You have very good detectors Co spreads out , your unit will detect it.
I use a Nighthawk Co- Ng leak detector digital display, 120- battery
backup. The nice thing about digital display is the memory high level
function, it allows you to monitor low level peaks that won`t alarm the
system but are a danger sign that something is going wrong. What you
have works. Low levels that don`t alarm will indicate Co from cracked
exchangers, blocked chimneys etc . You can get headaches from low level
even though it won`t alarm.