Keeping the door seal clean, unobstructed and intact helps to keep the ULT freezer chamber at the desired set temperature and reduces the build up of ice.

The action taken to obstruct the door seal is shown below. (left) Securing the 45cm long ruler to the top left-hand side of the opened freezer created at 3.8mm gap (right) between the door seal and the freezer chamber.

The obstructed seal spanned the entire height of the top freezer compartment (1) and ~50% of that of compartment 2.