Gas Sensor -- polarity

I have a MQ-7 gas sensor and the MQ gas sensor carrier.
I am trying to find the ground pins on the gas sensor, because if the gas sensor is inserted backwards, it will certainly break. However, I do not find any indication on the sensor or in the documentation.
please help.


Nope. Unlike most electronics, there is no wrong way for you to put the gas sensor into the Pololu Carrier. From the product page:

- Ryan