Question about Ei Electronics Ei208iDW Carbon Monoxide Detector

The audible alarm triggers with persistent CO concentrations according to these limits: 30 ppm: no alarm before 120 minutes; 50 ppm: between 60 and 90 minutes; 100 ppm: between 10 and 40 minutes; 300 ppm: within 3 minutes. A pre-alarm is activated above 43 ppm with the red light flashing; the higher the level and the exposure time, the faster the alarm.