Fangrui Product Details Body Worn Co2 Monitor: Make Of High Quality Abs, And Anti-fall. Both Sides Hollow Design, Easy For Air Come In To Touch Ndir Sensor To Detect Co2 Data. Back Case Hollow Help For Heat Dissipation Of Battery, To Keep The Measurement Accuracy. In Addition, Compact Size Body With Colorful Lcd Screen Digital Display, Clear Numbers, Easy To Identify And Read. And On The Top Of Co2 Meter Design A Hook Up, Easy For People To Carry And Bring Anywhere. Necessity Of Co2 Monitor: Carbon Dioxide (co2) Is Not Harmful To Human Body When It Is Low, But When It Overs A Certain Amount, It Affect The Breathing Of Humans (and Other Organisms). If Serious, Life Is Threatening. Thus, We Have To Monitor The Co2 Content Of Air For Keeping Health. Advanced Ndir Technology: Mini Co2 Meter Uses High Precision Ndir Sensor Technology (ndir Sensor Has The Characteristics Of Selectivity,anaerbic Dependence And Long Service Life) To Detect Carbon Dioxide Accurately And Quickly; Hazard Assessment : The Alarm Be Issued Once The Set Value