The new AirSense Model 350 delivers reliable and hassle-free carbon dioxide (CO2) sensing. You know us as a leader in CO2-sensing, but the Model 350 is the strongest, most reliable, and most versatile product we have ever offered!The Model 350 employs our patented single button calibration, which makes field calibration a snap. but please do not be disappointed if you never need to use this easy calibration feature, because the Model 350 is engineered to give you the best stability available in a low-cost PPM CO2 sensor!