Great little weather station. Keeping up with CO2 in a basement office can be very beneficial to long work hours. You can see the CO2 rise almost immediately after lighting a candle and such. 4-star because of poor packing. Batteries were not contained within the plastic bag (very large cut through bag) and had them rattling all over. Otherwise would've been a 5. Just appears to be a poor attention to that detail, where as all other details are stellar!