I've got a Carbon monoxide detector hanging in my kitchen for a few years now. Lately I've noticed it reads a PPM of 0 (zero). Is this right? Doesn't the air contains around 400 ppm?
In other words, is my detector even working? I'm getting the feeling I should throw it out.
Best Answer
As stated in @jwh20 's answer, the question is incorrect - 400ppm isn't a commonly occurring level - but it's a great question in that it brings up testing your alarm.
I think it's a legitimate concern. If something is important, it's important to test that thing. The self-test button is better than nothing, but it does nothing to test the sensor, it is a self test of the electronics. (And in general you can never really trust a self-testing device - if device has failed or is defective, how do you know the failure or defect doesn't affect the self-test?)
You can do a crude test by making some smoke with an incense stick or a cigarette or something and flooding the sensor with smoke. Obviously not a great test but it might at least show that the detector sees something.
Doing any better gets complicated. To test the ppm level display on the alarm's LED readout, you'd have to expose it to CO in a controlled environment and compare the alarm's readout to a calibrated CO meter. That's going to be well beyond DIY.