So I tested out the flexDF. I held it near a gap in the steel enclosure (behind the keep-out fencing) where the field was strongest for three minutes, and then moved it around erratically in the vicinity for a few more minutes. After the testing the Taginfo app read the same information as it had before the test. I would say it’s safe to assume everyday users are never going to need to worry about EMF damage to the tags.
I collected some data for posterity, even though it may not be the most reliable. A magnetometer app on my phone read 850μT from the spot I tested, which is nothing considering my teensy N52 magnet was registering 2000μT. That reading was almost certainly inaccurate because the app had a disclaimer about magnetic fields generated by AC. Here is an image of the transformer label. The input was 13.2kV. The tag was about 3 feet away from the centroid of one transformer during testing, with a steel cabinet enclosure.
