Formaldehyde gas analyzer principle 2. 1, the instrument for two sensor electrode sensor, a series of advantage is that it has three sample extraction and diffusion type sensor probe. The sensor electrolyte is inactive, similar to the flash of the electrolyte and nickel cadmium battery. Without considering the battery damage or acid damage to the instrument. Sensors have a sealed gas storage chamber, which not only makes the sensor life longer, and eliminate the possibility of a reference electrode pollution, no need air to operate the disadvantages of the three electrode sensor, can be used in the anaerobic environment. Sample extraction sensor is high sensitivity detector, according to the type of gas, its more than 50200 times of the dispersive sensor sensitivity. This is crucial for measurement of low concentration gas conditions. Formaldehyde mg/m3 and PPM conversion relation: PPM = mg/m3; On the B/M type: B: standard condition the molar volume of the gas ( 00 c, B = 22. 4. 250 c = 24。 46 liters) M: (molecular weight of the material being tested Formaldehyde HCOH M = 30) Namely: PPM = mg/m3; 22. 4/30= mg/m3; 0. 74666 public health standard of formaldehyde concentration index as follows: 0. 12 mg/m3 according to the formula of the relationship of mg/m3 and PPM: 00 0 c. 12mg/m3=0. 0896 parts per million, 250 0 c. 12mg/m3=0. 0978 PPM appendix: 1000 PPB = 1 PPM.