A temperature monitoring device comprising a temperature flexure element, which can be flexed from an initial position and an initial temperature in a flexing plane in a predetermined flexing direction in the case of a change in temperature, wherein the temperature flexure element has a first latching element of a latching mechanism on one of the ends thereof, the temperature monitoring device has an indicator element in an initial state, which can be brought into a further state, the temperature flexure element, the latching mechanism, the latching element and the indicator element of the temperature monitoring device are arranged relative to one another in such a manner that the first latching element of the latching mechanism in the case of a change in temperature is displaced in the flexing direction relative to a second latching element of the latching mechanism so far that the first latching element and the second latching element with each other cause a blocking of the relative movement of the first latching element with respect to the second latching element counter to the flexing direction, and that in the case of a subsequent change in the temperature towards the initial temperature and the therefrom ensuing resetting of the temperature flexure element and of the latching mechanism connected thereto, the second latching element is transferred by the indicator element, preferably irreversibly, from the initial state into the second state, characterised in that a) the indicator element is configured as a glass fibre rod and the second latching element on the side thereof facing the glass fibre rod has an element for breaking through or cutting through the indicator element, wherein the second latching element breaks the rod and thus the glass fibre line when the temperature flexure element is reset, b) that the indicator element is an electrically conductive rod, wherein the indicator element consists in particular of graphite and on the ends thereof is connected in each case to an electrical contact (4a, 4b) in an electrically conductive manner and that the second latching element, when the temperature flexure element is reset, applies flexure to the rod and thus interrupts the electrical connection between the two contacts and, and breaks the rod in particular, or c) that a viewing window is provided, through which the indicator element is visible, wherein the indicator element is configured as a container containing a fluid, and that the second latching element, when the temperature flexure element is reset, opens the container so that the substance escapes and is visible in the viewing window, wherein the substance produces a coloured reaction in particular with a substance applied to a viewing window. a) the indicator element is configured as a glass fibre rod and the second latching element on the side thereof facing the glass fibre rod has an element for breaking through or cutting through the indicator element, wherein the second latching element breaks the rod and thus the glass fibre line when the temperature flexure element is reset, b) that the indicator element is an electrically conductive rod, wherein the indicator element consists in particular of graphite and on the ends thereof is connected in each case to an electrical contact (4a, 4b) in an electrically conductive manner and that the second latching element, when the temperature flexure element is reset, applies flexure to the rod and thus interrupts the electrical connection between the two contacts and, and breaks the rod in particular, or c) that a viewing window is provided, through which the indicator element is visible, wherein the indicator element is configured as a container containing a fluid, and that the second latching element, when the temperature flexure element is reset, opens the container so that the substance escapes and is visible in the viewing window, wherein the substance produces a coloured reaction in particular with a substance applied to a viewing window.