Feature:1. [Quick Response] High accuracy carbon dioxide sensing elements, large measurement range and short response time, which is simple to use.2. [Simple To Use] The perfect choice for monitoring indoor ar quality (IAQ) and HVAC system performance, so you can use it with confidence.3. [Multipurpose] With large LCD screen, which can display carbon dioxide, temperature, humidity, time and date, to meet your various need.4. [Alarm Display] The quality monitor has alarm sound and alarm display, and the value can be set by yourself.5. [Widely Application] Carbon dioxide detector is widely used in a variety of situations, such as offices, bedrooms, living rooms, gymnasiums, etc.How to Use:1. Low alarm value setting: long press the "M" key to enter the low alarm value setting page. The display shows "LO" and the value is flashing. Press the "+" key to increase the value, press the "‑" key to decrease the value, the unit is 100PPM, and the adjustable range is 400‑4000PPM. After the numerical input is completed, short press the "M" key to complete the setting of the low alarm value and enter the setting of the high alarm value.2. High alarm value setting: as shown in Figure P2 below. The&nbs