my alarm peeps every min or so, only two lights on were the operating green light and the red alarm light which flashed on with the peep. I cant find my muanual. I have replaced the unit with new battereis and the unit's peep was replaced with a loud continuous siren sound. does this mean we have CO levels in our house? or is there something more I need to do with the unit after installing the battereis, maybe hitting the reset button?