Formaldehyde HCHO Thermo Hygrometer Meter Parameter: HCHO (CH2O), Temperature, Humidity RH% with USB Interface HCHO measurement: Range (0.00~5.00ppm) Accuracy (5% of reading) HCHO high alarm threshold setting with audible beep Alarm / HCHO self-calibration function (0.00ppm) at fresh and no HCHO environment Hold function, freeze readings, and battery low icon indication / Display Maximum, Minimum and recall function Triple large display: HCHO, Temperature/Humidity measurement w/ backlight function for working in dark area