4 in 1 gas detector can detect (0-100% ), H2S (PPM), O2 (0-30% VOL), CO (PPM), where refers to the concentration of combustible gas in the air, PPM (means parts per million concentration). When the dangerous gas content in the air is too high. Gas monitors will remind you that the place is dangerous within 30S through four methods: human voice, 120 decibel alarm, vibration and light.Multi gas monitor has an LCD display that allows you to easily read the screen data, the readings are very reliable, it is an excellent device to ensure the safety of workers when we are undergrounding construction and confining space work. We use 1800mAh high-capacity lithium battery to ensure that the product can be used for a long time.Good shock resistance, dust-proof, waterproof and explosion-proof functions. When you are in a closed or hypoxic environment, you don' want it to sound the alarm all the time, all four gases can be adjusted to your desired threshold (within the range).PACKING1,Multi Gas Monitor.2,Stainless Steel Clip.3,Calibration Cap and Screw.4,USB Charging Cable.Colour:blackMaterial:ABSPackage Contents:1 set x h2s Multi Gas MonitorOnly the above package content, other products are not included.Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.