... Specifications 1,Self-testing anytime;2, Alarm memory & query record function;3, LCD display concentration (3 digitals);4.Three LEDS to indicate different ... & LED indication); 6.Test/Hush/Reset Button with 3 LEDS 7. Low Battery alarm (alarm,LCD display $ LED indication)8, Can not be ... ~ 40 minsAt 300 ppm, unit must alarm within 3 minsUL2034:At 70 ppm, unit must alarm within 60 ~ 240 minsAt 150 ppm, ...