Hi guys. I recently purchased a CHHC-1. When switching CO2 on, it make a pretty loud "pop", sounds almost like an electrical high voltage spark. Turning off also makes a sound, but not nearly as loud. When the CO2 turns on, I can hear it in the living room ~ 25 feet away through a wall, clearly. Another problem I have had is with the humidity sensor. It seems to be accurate sometimes, but others it drops down to the teens or 0 RH when it is clearly ~50-70%. Anyone have any input? I'm thinking I might need a new sensor or something. I'm going to contact the guy I bought it from to see if I can get the receipt, as it is apparently about 8 months old.