How can i figure out MQ135 pins?

Sorry for poor english
I buyed an MQ135 air quality sensor, I'm trying to communicate with Arduino Nano but I cant seperate pins;
Which side is A-H-A, which side is B-H-B?

You can use your multimeter to determine which pins are H.

Thanks for answering, but solved :slight_smile:.

The right schematic shows you what you need to know. A-B directions same, H too.