Digital display- displays the level of carbon monoxide the unit is sensing. Automatically dims in low light conditions. Sealed Lithium Battery Backup- 10 Year tamper proof battery eliminates need for battery replacement. Alerts User to replace alarm after 10 years of Operation Peak Level Memory- Displays the peak CO level recorded since its last reset End of Life ALarm- Alerts user to replace alarm after 10 years of operation. Can be temporarily silenced for convenience. No Night Chirps- End of life and low battery signals programmed not to occur in dark conditions, hekping to prevent needless waking of user.