GROVE - GAS SENSOR(MQ-9) [CALCULATE PPM]

Using Arduino Sensors
#1

Hi,
I'm using the MQ-9 grove sensor for a project on indoor air quality with Arduino Uno Wifi.
I'm following the guide from this site:

http://wiki.seeed.cc/Grove-Gas_Sensor-MQ9/

I would have two questions to ask.

  1. What is meant by:'Keep the Gas Sensor in clean air environment'? Can I leave the sensor in my room?

  2. After determining the Rs / R0 ratio, I am unable to determine the concentration in ppm of the 3 individual gases (LPG, CO, CH4) by having the graph at the end of the linked page. Is there a way to determine it for each gas?

I hope you can help me and thank you in advance.

#2
  1. Yes. clean air means normal working environment (no ‘gas’)
  2. No. The sensor doesn’t tell which gas is present.

You will find several posts relatetd to MQ7,MQ9 sensors. (some code too)

#3