Abstract: A system and method of protecting production tooling used in semiconductor fabrication from potentially damaging low temperatures or sudden temperature drops during periods of primary power outage and low outside temperatures. The boilers and pumps at a central utility plant (CUP) which normally provide superheated water under pressure to heat exchangers in each building to be heated are cut back to a fraction of their normal heating capacity during periods of primary power outage, although air continues to be exhausted from, and outside air taken into fabrication buildings. In the present invention, an additional heat exchanger is placed in each building which houses production tooling, and the coolant from the engine used to drive the generator for powering the air handling equipment in the building may be selectively directed through one of the flow paths of the second heat exchanger.