Need recommendation on which gas sensor can be used

Other Hardware Sensors
1

I need analogue values for the following gases, for a project. Please recommend some sensors that can be used for the same and compatible with arduino.

  1. Hydrocarbons
  2. CO
  3. NOX
    4 CO2
  4. Smoke

Thank You.

2

You could buy an industrial calibrated measuring apparatus for thousands of dollars.

For the Arduino the MQ sensors are often used. But they can not detect a certain gas, they detect a number of gasses. Therefor they can be used for air quality, but not to determine amount of a certain gas.

Another major disadvantage of the MQ sensors is that they require a certain amount of current for the heater and the sensor gets hot.
http://playground.arduino.cc/Main/MQGasSensors
If you buy a few of those sensor on Ebay for a few dollars, you can check for yourself how they behave.

If you want accurate values for the different gasses, it's gonna cost a lot of money. If you want to have a number for the air quality, the MQ sensors are cheap, not accurate at all, but very sensitive.