I suggest First Alert CO400 available everywhere including Wal-mart. All CO detectors sold by major US retailers meet US government standards for when to alarm to warn you. Important thing is if they go off, leave the area immediately and get the situation evaluated by a fire department or a heating system professional, BEFORE you re-occupy the area.
There are some with displays that will indicate highest CO level seen by the detector, but these are generally 120 volt AC powered, so may not suit use in a RV.
With carbon monoxide, it is the concentration of CO over time that poses a threat. Since carbon monoxide displaces oxygen in your blood, it can harm you if you are exposed to either high levels of CO in a short period of time, or to lower levels of CO over a longer period of time. Current UL limits for CO exposure are:
o 30 ppm (parts per million) for 30 days
o 150 ppm for 10-50 minutes
o 70 ppm for 60-240 minutes
o 400 ppm for 4-15 minutes
CO is a odorless colorless gas you can't see it or smell it. All, use that test button on the CO detector occasionally and make sure your detector is powered and ready to warn you.
Randy - Manhattan, Kansas
2015 Vista 27N
2016 Honda HR-V