Rojo
The only thing I know about RF safety goes back to the issue of health risks from mobile phone use. If the radiating frequency falls into the non-ionizing band ie RF rather than microwave & higher, the only requirewment is that the bulk heating effect of the RF should be below an internationaly agreed limit (which I don't recall).
Because the hazard is only tissue heating there is no concern about possible cumulative effects so there isn't a temperature/hours limit.
There are similar requirements, for the same reason for ultrasound energy.
Marc
