abstract the operation of a combustible atmosphere furnace is controlled by monitoring the temperature of the combustible atmosphere and the rate of change thereof the measured rate of change is compared to a previously determined safe rate of change so as to anticipate and discourage incipient internal ignition application_number US 76993491 A description referring now to fig1 furnace 20 is shown to comprise oven 22 oven door 24 firing chamber 26 afterburner chamber 28 and stack 30 in this application contaminated parts 32 are conveniently contained in wheeled cart 34 which facilitates the charging and discharging of furnace 20 flow paths 35 36 and 37 indicate the flow of heated gases from firing chamber 26 through parts 21 and into afterburner chamber 28 during operation of furnace 20 as parts 21 are so heated the contaminates vaporize and become constituents of combustible atmosphere 40 in fig2 is shown an embodiment of the present invention as used for the safe control of furnace 20 in a manner which anticipates and avoids ignition or explosion of combustible atmosphere 40 this view is taken from the direction of arrows 2 2 of fig1 and also allows a more complete understanding of the operation of furnace 20 here firing chamber 26 is shown to include burner 44 blower fan 45 and outlet 46 similarly afterburner chamber 28 includes blower fan 49 burner 48 and inlet 50 furnace 20 is fired by engaging master switch 60 to open firing chamber burner valve 43 and afterburner chamber burner valve 47 this admits fuel from supply line 42 which is ignited by conventional pilot flames as is well known in the art the operation of firing chamber burner valve 43 is also.