Shielding a room using aluminum foil

A local hospital was interested in shielding some sensitive equipment and contemplated installing a shielded room. The room under consideration was the typical laminated wood core panel with galvanized steel on both surfaces, with a RF shielded door, honeycomb air vent panels and filters for ac power, telephone and any other signals, meeting the shielding effectiveness requirements of MIL-STD-285 or IEEE 299-1997. As schedule was important, a room was purchased and installed. However two interesting questions have been raised 1) How much shielding effectiveness (S.E.) was actually required and 2) Could the existing room be converted to a shielded room and if so would it be less expensive than the conventional shielded room within the room. This report does not set out to answer the first question as factors such as the level of electromagnetic ambient and sensitivity of the equipment to power line conducted noise, E fields, plane waves or magnetic fields remain unknown. Another deciding factor is the frequencies at which the equipment is susceptible. Instead the conceptual design for a room covered in thin aluminum foil is described and the predicted shielding effectiveness for magnetic fields, plane waves and E fields are measured and predicted. Some estimated costs are provided although the final cost must depend on the size of the room, the cost of local labor and the type of finish required on the walls and ceiling. It is worth reiterating that whether the level of predicted shielding achievable with this type of room is adequate depends on the level of the electromagnetic ambient to be shielded against and the susceptibility of the equipment to be shielded. This may be determined by localized shielding of sensitive equipment using aluminum foil or by analysis, although this is more difficult. This susceptibility will almost certainly vary with the type of field and the frequency. One word of warning, medical equipment is often susceptible to the emissions from fluorescent lights and if either the conventional shielded room or aluminum foil shielded room is provided with fluorescent lights it is important to also include alternative lighting such as filament lamps and to use a separate switched circuit for the fluorescent lights. Apart from cost, the aluminum foil has the advantages of being potentially aesthetically more pleasing than a typical shielded room and in fact if the walls are properly covered and the floor covered in tiles, it will not be obvious that it is a shielded room. Another advantage is that any size room may be shielded without reducing its size, which typically