The premium choice for use as a primary alarm with digital readout of CO levels. Digital Readout - Continuous display of CO levels. Battery Backup - Continuous protection in case of power failure. Peak level memory - Recalls the highest recorded level of CO.. Test / Reset button - Tests circuitry and resets alarm. Electrochemical sensor - "The world's most accurate sensor". *This product is Recertified. A recertified product is one that is returned by a customer, for whatever reason, and then restored to original working condition after undergoing an intensive inspection process by qualified technicians. The recertified product is then offered at a substantially discounted price. All stock of our current products are guaranteed to be in working condition and have been successfully tested for optimal performance. 7 day return policy is in effect for both in-store and online purchases. See in store for more details.