multi zone furnace overtemp limits

[joecontrol]

I am looking for some help on the upgrade of a multi zone car bottom furnace. I cannot get a direct answer on if i need a temp limit for each zone or if i can monitor the whole furnace with one thermocouple with one limit controller. For info no one zone has enough BTU's to push the furnace over the designed temperature limit.I am trying tp upgrade a furnace built in the 1950's. Up to a resonable saftey system without the expense of going to the full NFPA my employer does not want to spend the $$ and is not being forced to by osha or an insurance company.
Total BTU's is 12 million btu/hr each zone is 4 million btu/hr.
I would like to add pressure switches(gas high&Low,Comb air)Temp limit and & purge system & low fire start .With flame saftey relays at each burner.
Thanks,Joe