digitalWrite(led_red_pin, m.co2_ppm >= co2_alarm_thr);
digitalWrite(led_yellow_pin, m.co2_ppm >= co2_warning_thr && m.co2_ppm < co2_alarm_thr);
digitalWrite(led_green_pin, m.co2_ppm < co2_warning_thr);
digitalWrite(led_red_pin, m.co2_ppm >= co2_alarm_thr);
digitalWrite(led_yellow_pin, m.co2_ppm >= co2_warning_thr && m.co2_ppm < co2_alarm_thr);
digitalWrite(led_green_pin, m.co2_ppm < co2_warning_thr);