Abstract: A detachment system includes a first piece of ferromagnetic material, a shunt plate, and at least one simple machine. The first piece of ferromagnetic material has a first side and a second side opposite the first side and has magnetically printed field sources that extend from the first side to the second side. The magnetically printed field sources have a first multi-polarity pattern. The first side of the first piece of ferromagnetic material is magnetically attached to a second piece of ferromagnetic material. The shunt plate is disposed on the second side of the first piece of ferromagnetic material. The shunt plate routes magnetic flux through the first piece of ferromagnetic material from the second side to the first side of the first ferromagnetic material. The at least one simple machine is configured to amplify an applied force into a detachment force to create an angled spacing between the first piece of ferromagnetic material and the second piece of ferromagnetic material.

Abstract: A heat exchanger for energy efficient ventilation of buildings is described. The heat exchanger has a core structure defined by a plurality of rectangular sheets of an extruded, cellular plastic material disposed in parallel, spaced-apart relationship. The cells of the sheets provide a first set of flow paths extending between ends of the core structure for use in passing cold fresh air. The spaces between the sheets are sealed at each end of the core structure, and a cellular plastic sealing material is wrapped about the sides, top and bottom of the core structure and apertured at opposite ends to access the spaces, so that the spaces between the sheets define a second set of flow paths for passing stale warm air. A drainage aperture is provided in an inner face of a bottom sheets of the sealing sheet, where condensation tends to accumulate. The drainage aperture permits condensation to escape through the cells of the bottom sheet.