MQ 9 carbon monoxide sensing

I am wanting to use mq9 sensor for measuring carbon monoxide, as per the data sheet im giving it a 1.5v supply but the readings coming ro for 0 and ro/rs is infinite, also in the code( which is provided for lpg where is the value rs/r0(9.9) coming from? how do i determine that for C0?
If there is a different code for CO please mention it here,
thank you.

The supply voltage for Grove mq9 is 5V as per the data sheet please use this and let me know if it works.Can you please give information about the microcontroller development board that you are using.