As Justin already stated, CO and propane require two different types of detectors. Whilst there may be some units that combine two detectors in one unit, they are still separate device.
The good news is that propane is odourised so that the best detector is just your nose.
Natural propane is odourless but an odorant is always added for normal applications.
On the other hand, CO - carbon monoxide - is odorless, so a detector would be required if there is the possibility of generating dangerous levels in an enclosed space.
The following is form my blog and explains the propane side of the issue:
The LPG Smell of Safety – Odourised Gas
In their natural state, LPG (Propane and Butane) and Natural Gas (Methane) are all odourless gases.
The distinctive smell that people associate with these gases is actually added to them as a safety measure.
History of Adding Odourant to Gas
For many decades, the gaseous fuels industry has added odourants to LPG and Natural Gas so that people can detect gas leaks with nothing more than their noses.
Without the addition of an odourant, leaking gas could collect without being detected.
This would create a dangerous condition that could lead to an explosion or fire.
Much research has gone into the science of odourants and Ethyl Mercaptan is almost universally recognised as the best choice.
As a result, it is the most commonly used odourising agent.
The smell of Ethyl Mercaptan is often compared to rotten cabbage.
You need to buy a co gas detector.
Size: 114 mm*55mm*46mm
Weight: 105 g
Sensor types: Electrochemistry method
Destination gas: oxygen (O2), toxic or harmful gases (CO, H2S, NH3, CL2, etc.)
Response time:≤40s(CO)
Display: segment LCD, high brightness yellow backlighting
Alarm: voice alarm More than 90 dB voice alarm (10 cm away from instrument)
light alarm Red LED
Temperature range: - 20 ℃ ~ 50 ℃
Humidity: 15% ~ 95% RH (No condensation)
Battery type: CR2 CR15H270 lithium battery
Power supply: 1 High-energy battery (Replaceable)
If you are interest in it, please contact anna@huafankj.com