Just to add about the pacemakers... More than once we had to stop everyone who was GTAW Al with hi-freq in the Lab or even just using it in the start mode because, someone in an adjacent classroom of the same building, had a pacemaker...
The first time which happened approximately 5 years ago, the individual I spoke to mentioned to me that his heart rate was jumping erratically all over the place, and he felt like he was hooked up to a defribillator with a madman under control of it!!!
Well needless to say, after that incident the school policy was changed so that every student had to let the school know whether or not they had a heart pacemaker or any other electronic device implanted within their bodies, or attached to an external device, so we could accommodate them by not having any of the hi-freq run whether it was on in the starting mode, or the continuous mode during the sessions the individuals were scheduled to be in class at the same time we were in the lab until we finished properly shielding the lab from leaking anymore high frequency into the rest of the building... Thank God the first person did not sustain any permanent injury as a result of the leakage exposure.
Signs are now posted in every entrance or exit clearly stating as a warning to all individuals connected to any internal or external electronic device associated to sustaining their health, must report it to their instructor immediately before starting any course in the building... The sign continues to state that failure to report their condition to the school at all, prior to the start of any course will expose them to potential trauma that may be lethal to them... We have since repaired the leakage however at any time, someone may tamper with the shielding so we came to the conclusion to keep the signs up everywhere - just in case!!! ;)
In summary, I would strongly suggest to anyone involved with welding training or education that Hi-frequency is nothing to take lightly, and to double check their own shielding especially if you have an educational environment where in different parts of the building, other classes are being scheduled to run while the welding lab is in use...
Post warning signs at all entrances and exits so these other students are made clearly aware time, and time again of the potential dangers to them, so that the school can accommodate by scheduling their class in another building for them at least until the leak is repaired, or they can insist on having their classes in another building while the welding lab is being used during their scheduled class sessions simultaneously.
Also, to warn them via continuous monitoring before the start of any lab session, whether or not the lab is fully shielded and therefore, the building is safe for person's with these devices. We also have a policy of discouraging anyone with a pacemaker or any other electronic device no matter which brand name, from enrolling in anyone of our welding courses - PERIOD! Regardless of the most current data on some of these devices and simply put, to protect ourselves from any potential liability.
Respectfully,
Henry