What are the components symbolized in these 4 highlighted areas of this schematic?
J177 P-channel JFET
R3 resistor 20K
RT1 thermistor 10K at 25°C
U1A/U1B the halves of a dual op-amp
R3,RT1,R5 form a temperature-dependent resistance to help temperature compensate the gas sensor output.
You should credit Zhengzhou Winsen with the graphic you copied.