Hello,

"how difficult?" - depends...

... primarily on two topics

Regarding implementing a calibration facility, you will need either 

• pre-mixed test gases ('gas standards'). This is surely the most expensive solution, but it eases the setup of the calibration facility: only gas flow control in an on/off scheme is required.   or
• pure test gases plus so-called "mass flow controllers". There is one supplier of these mass flow controllers I know of: Bronkhorst High-Tech B.V. (http://www.bronkhorst.com/). Others may exist, but the "Bronkhorst's" are what was used in my environment.

Mass flow controllers can be calibrated. Anyway, much of your results depend on the purity resp. quality of the test gases.

Don't know about the gas supply situation in India (a critical parameter), but calibratable mass flow controllers should be available. Even if shipped from Germany :) In addition you will need the control equipment including 'good quality' gas control valves. But this should not really be an issue.

My greetings to you and the colleagues from RBIN