Guidelines For Limiting Radiofrequency Exposure - Short Wave Diathermy - Safety Code 25

3. Recommended Maximum Exposure Levels in Canada

Short-wave diathermy devices operate predominantly at a frequency of 27 MHz. The maximum levels recommended by Safety Code - 6(4) for "occupational exposure" of workers in federal establishments at these frequencies are as follows:

1. For whole- or partial-body exposure (including extremities - hands and arms, feet and legs) averaged over a one-minute period

ii. For whole- or partial-body exposure excluding extremities averaged over a one-hour period

iii. For a whole- or partial-body exposure (excluding extremities) for periods of exposure longer than 1 minute, but shorter than 1 hour, the maximum time, t (minutes), that a person can be exposed to the field must not exceed

t = 60/W,

where W (mW/cm²) is the equivalent plane-wave power density. The equivalent plane-wave power density corresponding to the electric field intensity E (V/m) and the magnetic field intensity H (A/m) is:

W = E²/3770,
W = 37.7 H²

iv. For exposure of the extremities averaged over a one-hour period

v. For exposure of the extremities for periods longer than 1 minute, but shorter than 1 hour, the maximum time, t (minutes), that extremities can be exposed to the field must not exceed

t = 600/W

where W (mW/cm²) is the equivalent plane-wave power density.