Now I would like to put in a plug for the Avallo Accumonitor. The Accumonitor is the only electronic humidification system that uses the Boveda for calibration. At home, you can use a Boveda to check the Accumonitors accuracy, and actually recalibrate your Avallo so that your humidity readings are perfect. The Boveda saved us about $15,000 because we did not have to buy a so called professional calibration chamber, and the bottom line is the Boveda gives better results. For $4, you can do at home what a calibration service would charge $100. we trust the BOveda 100% in calibrating our electronics.