Nighthawk Carbon Monoxide Detector

I was cooking in the kitchen today and I noticed the number obtained at 9, but the alarm did not work. I just want to know about these figures, I have no idea how the numbers go. Thank you for your help.

If you do not find the manual, try looking at your model on the Internet. * The numbers may indicate parts per million of CO detected. It is 1000ppm to cause unconsciousness in one hour, then 9ppm is not good, but it is considered "normal" background CO

Take a look at http://www.nfpa.org/itemDetail.asp?categ ... For more information.