Ever used an infrared massager? They emit in the far infrared range 4 - 1000 microns(4mm-1000mm)-just above what we are discussing. I wonder how long that method of therapy has been around?
Intrinsically safe, in my and most everyone's opinion, but to each his own.
Ah, heck. Let's just run everyone and their gear thru one of these.
Might be fun to go watch, even.
I had a friend who designed a super-heated steam radiant heating system for a local famous theater. I will count that kind of radiant heat as “experimental” — for whatever reason it burned people at a depth in the flesh they did not feel — at least until the burn had gotten bad. That opening night was not a happy one the few days following. He turned the temperature down before they booted him.
That story in based on his retelling of it. I never bothered checking it out.