Please help for MQ2 programming

I want to have the code for MQ2 gas sensor.

The Simple arduino MQ2 code.

When MQ2 gas sensor detect the gas (can be any gas but will use the hot water vapor) then the Fan will spin.

But can you help me to have the button switch to on and off this MQ2 sensor coding?

Working process:

button (on/off) -> MQ2 gas sensor detect the gas -> Fan spinning

Please help me !!

The MQ2 uses a lot of power all the time because you have to keep the heater running. I would recommend a DHT11 temperature/humidity sensor: http://www.adafruit.com/products/386

Post the code you already have.

...R