I bought two Honeywell BW Solo CO monitors for my two airplanes. One which I bought in January works fine but the other says battery flat. I bought batteries from RS and replaced it and it still says battery flat. I contacted Frontline Safety who informed me that I have invalidated the warranty by changing the battery and that I should return it and they will quote me for a repair. How on earth do you invalidate a warranty changing a removable battery?? I looked on the Honeywell site and it says that I have a two year warranty so I will return it to Honeywell and make a complaint about Frontline Safety. I would advise not to use this company and I will not again. The support person was hostile in all communication. Avoid them in my opinion. The measure of a good company is how they deal with a problem and this was a 0/10 experience.