I am slightly confused on Class A ovens in regards to electric heating and whether or not I need to purge the oven before starting the start up sequence. This is an electric infrared oven that cures painted parts at a temp of 150 deg F. This oven is an older oven without any high temp cutout, no temp controllers (based on timer relay to pull heating contactors in with a 9 sec on and 21 sec off.) I want to install 4 High temp controllers to cut out the heating if an overtemp condition occurs. From what I have gathered from the code, I will also need to monitor the exhaust blowers via press diff switch which would be interlocked with the heat to cutoff if they also fail. Please help me with interpreting the NFPA 86 code on this oven.