MQ gas sensor for calculating PPM values.

Hi all
I've got my major project and it employs the use of MQ gas sensors. After a lot of googling, what i couldn't exactly understand is how to calculate the sensor values in PPM. There are A LOT of articles on what needs to be done, out there but none of them has a clear cut say for a beginner to understand the right method.
On plugging the sensor, it gives some analog values, which can easily be mapped but that's not the real concentration of gas in the environment.
There is something written about calibrating the sensor as well, which is partly understood as Rs, Ro and RL, all start to confuse me.

Any guidance on how to proceed in an exact way would surely be appreciated.

You connect the sensing (R0 = n kOhm) resistor in serie with a fixed resistor RL (choose a value close to R0.
The graph shows you how R0 will change to a new value RS when gas is detected.
The curve is often a straight line in a log/log graf. That tells the function is a power-function.
You may also find a parameter 'alfa' (or 'gamma') that tells the slope rate og that function

Hi,

Could you explain to me why it is needed the RL and how to calibrate it? Thank you

RL looks very much like half of a voltage divider to me.

There are several MQ sensors. Which is it?