This is neat. Clive Robinson, “man of many brains,” predicted about all of this stuff on Schneier’s blog years before it happened. It seemed like he was going overboard but he got to the root cause. He said any matter or energy might be turned into a communications medium for leaks. So, we had to “energy gap” systems to block or mask as many forms of that as possible. Heat was one of them esp as we were discussing infrared techniques. Another I recall from that was you couldn’t have toilets in the shielded rooms since the pipes and water could carry the signals. Had to have a buffer with two doors and its own shielding to prevent leaks during entry or exit if the computers were still on. Then there’s ultrasound and other forms of sound.
List goes on. Most important of old rules was that nobody near a secure PC could have a cell phone on them. Even a dumb cell phone. Some models just connecting to the tower would reflect the master keys of secure devices such as STU-III in an accidental, active, EM attack. So, no wireless devices.