I must give praise when it is due...since my home is just about total natural gas I had 6 CO detectors in different areas of my house....2 of them were 2 years old...1 I was having problems replacing batteries every 3 months (should have lasted much longer) the are 110vac powered, however for emergency a 9 volt battery is used. The other was a CO and explosive gas detector (2 in one) that was doing great for 2 years, however it gave me an error message that told me to contact the Nighthawk company. I called Nighthawk's customer service and explained the problems with my 2 detectors, after asking for the inormation listed on the detectors...date..serial# etc. told me they would send me 2 new like detectors. In 5 days I had the new detectors in my hands from Nighthawk..... In this day and age of unreliable customer service, I think it is commendable of Nighthawk...there are other companies out there that have great service also, and I surely think we should know about them when their service excells
NIGHTHAWK C.O. DETECTOR (**********) 10 star rating in my book