Factories Act, TAC and IS2190 have not specified the specific fire protection systems.
You shall have to refer to Gas Cylinder rules, read MSDS and compile both the requirements and accordingly make the necessary preventive system.
Ammonia falls under Major Accident Hazard rules Schedule I part II serial number 31 of Maharashtra rules.
You need to have on site emergency control plan under these rules.
You are required to conduct the safety audit from the competent person and comply the suggestions.
I have never used toxic gases hence I may not be able to comment upon the sprinkler requirements.
Alternatively you can find out who else is using Ammonia and find out the safety requirements.
All said and done please update on this forum once you get the authentic suggestion.
Thanks & Regards,
13th July 2012 From India, Nasik