So, go hi-tech with ferrite foil, or lo-tech with a mild-steel biscuit tin...

' three different approaches can be put to use if one wants to prevent attackers from establishing the magnetic covert channel: shielding, jamming, and zoning.'

What would be the purpose of allowing personal cell phones in a Faraday-Caged, Air-Gapped computer room? The obvious solution is zoning - keeping personal devices half a kilometer away in a steel locker.