With a penetrating volume of 85 dB (A) and an optical signal in the form of LEDs, the X10-D.2 alerts you to increased concentrations of carbon monoxide. Green light indicates operational readiness, red light indicates an alarm state, and yellow light indicates a malfunction. The alarm itself is regulated according to EN 50291:2010 and is tiered based on the level of carbon monoxide concentration in the air: Concentration of 50 ppm (0.005%): 60 to 90 minutes until alarm activation, concentration of 100 ppm (0.01%): 10 to 40 minutes until alarm activation, concentration of 300 ppm (0.03%): less than 3 minutes until alarm activation.