9.13.1 ELECTROMAGNETIC RADIATION

Human exposure to electromagnetic (EM) radiation at certain power-density levels can be hazardous. The hazards are generally regarded to be associated with the heating of biological tissue, which occurs when EM radiation is absorbed by a body. This heating is essentially similar to the cooking process in a microwave oven. Use caution where EM sources are being used with the shielding altered or removed.

When working with EM radiation, it is recommended that the emitted radiation levels be estimated by equations and measured by radiation hazard monitors.

EM radiation-safe levels have been established by the Institute of Electrical and Electronics Engineers and are documented in the IEEE standard - C95.1-1991.

Exposure to hazardous levels of EM radiation can be lessened by maintaining as much distance as possible from the source. Power density is reduced by a factor of four by doubling the distance from the source.

9.13.2 ELECTROMAGNETIC RADIATION THREAT TO ELECTROEXPLOSIVE DEVICES

Designers of enclosed electrical/electronic equipment must consider the possible effects on nearby electroexplosive devices (EED) of electromagnetic radiation (EMR), i.e., radio frequency (RF) energy, emitted by that equipment.

Energy induced into an EED by the electromagnetic field resulting from such emissions may be adequate to cause the device to detonate.

Factors which should be taken into account in assessing concerns for possible EMR emissions are:

1. Wiring, shielding, and sensitivity 2. Proximity

3. Frequency of the emissions causing coupling of electrical energy 4. Power density

5. Type of emission modulation

Possible measures to mitigate the threat of EMR emissions include:

1. Enclosure and signal line shielding and grounding to prevent leakage of EMR from the equipment.

2. Designed-in physical separation or barrier which would ensure that the power density of the electromagnetic field is inadequate to cause detonation of an EED at the closest possible distance to the emission source within the equipment.

3. Filter, or provide ferrite beads for, signal lines from the equipment which may conduct EMR emissions into EED circuitry or secondarily radiate EMR in the proximity of an EED thus causing a threat of detonation.

4. Ensure that the minimal power necessary is used to operate circuitry capable of producing EMR.

5. Label the equipment capable of emitting EMR to indicate the minimum separation distance to be maintained between the equipment and an EED(s).