I was wondering about carbon monoxide detectors, if a gas cooker was left on for a long time would it be detected?

Thanks

Carbon monoxide is produced whenever a fuel such as gas, oil, kerosene, wood or charcoal is burned. The amount of CO produced depends mainly on the quality or efficiency of combustion. A properly functioning burner, whether natural gas or liquefied petroleum gas (LPG), has efficient combustion and produces little CO. However, an out-of-adjustment burner can produce life-threatening amounts of CO without any visible warning signs. When appliances that burn fuel are maintained and used properly, the amount of CO produced usually is not hazardous. But if appliances are not working properly or are used incorrectly, dangerous levels of CO can collect in an enclosed space. Hundreds of Americans die accidentally every year from CO poisoning caused by malfunctioning or improperly used fuel-burning appliances. So the answer is YES, if dangerous levels of CO can collect in an enclosed space over time and you have a carbon monoxide dectector that is in good working condition it should be able to detect the gas admitted by a "gas cooker".

A properly adjusted propane of NG flame will not set off a carbon monoxide detector. Your terminology, gas cooker, probably needs to be better explained. What is it exactly?