Modular furnace, in particular for the oxidative stabilization of a carbon fiber starting material

A modular furnace comprising a rectangular-block shaped furnace chamber, first deflection rollers being disposed so as to be mutually spaced apart and mutually parallel on the upper side of the furnace chamber, and second deflection rollers being disposed so as to be mutually spaced apart and mutually parallel on the lower side of the furnace chamber in such a manner that the carbon thread starting material in the furnace space of the furnace chamber runs side-by-side and mutually slightly spaced apart in a meandering vertical up-and-down manner, a carbon thread entry lock installation and a carbon thread exit lock installation provided on the upper side of the furnace chamber, an air guiding installation which by way of an intake air portion is connected to a vertical air entry side of the furnace chamber and by way of an exhaust air portion is connected in fluidic terms to a vertical air exit side of the furnace chamber that is opposite the vertical air entry side being connected to the furnace chamber, and the air guiding installation having an air driving installation between the intake air portion and the exhaust air portion and wherein the modular furnace comprises an air exchange installation which has a fresh air inlet and an exhausting air outlet and in that at least one gas sensor is operatively linked to the fresh air inlet and to the exhaust air outlet of the air exchange installation which is provided in the exhaust air portion and/or in the intake air portion of the air guiding installation.