Abstract: A bracket member of square U-shaped configuration having first and second spaced parallel arms and a head joining the arms and extending perpendicularly thereto rests on a wall of a freezer at the opening of the freezer with the first arm abutting the outside surface of the wall, the second arm abutting the inside surface of the wall and the head abutting the edge of the wall. A battery and an alarm are mounted on the first arm of the bracket member. A thermometer device is mounted on the second arm of the bracket member and has a column of mercury for indicating the temperature and a pair of spaced electrical contacts in the path of the column of mercury at an unsafe temperature. Electrical conductors connect the battery, the alarm and the thermometer device in a circuit whereby when the temperature in the freezer becomes unsafe as indicated when the column of mercury reaches the electrical contacts, the circuit is closed and the battery energizes the alarm.