How best to check a furnace for leaking carbon monoxide

[hvac meister]

I've heard so many different opinions on how to check for CO. Is it best to check right at the supply plenum? Or at the closest supply register? Also, how long should the furnace be running before you get the best results? And while I have your attention(lol)..... which are the best handheld CO detectors out there?
Thanks in advance........

[second opinion]

Invest your money in a quallity combustion analyzer and training on the combustion process, then test and adjust the system with it.

[davidr]

Invest your money in a quallity combustion analyzer and training on the combustion process, then test and adjust the system with it.

Great advice!

Testing in the supply airstream won't give you a whole lot of information but testing in the flue gas itself is where the real answers are.

[RIGUY]

combustion analyzer or old school combustion test kit and knowing what your looking for in terms of your measurements. You will succeed. look for cracks in the heat exchanger and look at the flame should be going up unless it tabulators.

[i b cool]

Attend NCI combustion analysis training class, in 3 days time you will have all the answers.

[sensorconmark]

If you're just looking to measure CO, take a look at the CO Inspector Kit from Sensorcon. I've taken measurements from the exhaust from furnaces, hot water heaters, and even exhaust from cars (after the catalytic converter has warmed up some). BTW, if anybody cares anymore, the CO Inspector is the only CO meter/detector/monitor that I know of 100% designed AND made in the USA (I've read prior posts where another manufacturer mentions designed in US made in Taiwan, which is kind of insulting in my opinion).

As for combustion analyzers, you'll pay more $ (a lot more) but will get more info. Most of them I've seen only measure O2 & CO, and calculate CO2/efficiency based on those measurements and the type of fuel. More expensive systems will actually measure CO2 with an additional CO2 sensor. I'm curious if anyone has experience with both styles, and if so, have you ever run into cases where the calculated CO2 level is inaccurate? (since after-all it's just a calculation, not an actual measurement).