Interesting fact is to look up “CO detector alert level”. They can take 10 minutes or more to sound at 100ppm, a few minutes at 400ppm.
As pointed out in another thread (not specifically about this article) the article actually addresses CO alarms. Detectors of any sort merely signal silently a remote location (alarm services) what is needed in a home is an alarm which emits an audible noise to alert the occupants.