Castor wheel assembly including a castor pin having a castor axis; a yoke mounted to the castor pin\u2014and rotatable about a yoke axis; a castor wheel rotatably mounted to the yoke about a wheel axis; and a gradient device disposed between the castor pin and the yoke. The insulating board has plural switch-contacts. Opening the door activates the dead bolt and sounds the alarm. The upper portion includes a hooked section having a first width smaller than a width of the narrower portion and a second width perpendicular to and larger than the width of the narrower portion. The output system allows for the transfer of air from the exterior zone to the external environment, re circulates the air back into the return system or re-circulates the air back into the intake system.