How can I impalement only gases file like Ar , CO2 or N2

Garfield++
1

how can I impalement only gases file like Ar , CO2 or N2 ?
how can I get induced electric field ?

2

Implement gases in what sense?

3

By using gase file or a function

4

If your question is about how to create a gas file, maybe this helps:
https://garfieldpp.web.cern.ch/garfieldpp/examples/gasfiles/