You can receive an RFR burn if your skin contacts a source of RFR voltage. This is because your skin's resistance to the current flow in the area of contact produces heat. The effect of this heat on your skin can range from noticeable warmth to a painful burn.

Mild RFR burns are usually indicated by small white spots on the skin and possibly the odor of scorched skin. More severe burns may penetrate deeper into the flesh and produce painful and slower healing injuries. For our purposes, "hazardous" will be associated with the RFR voltage level sufficient to cause pain, visible skin damage, or an involuntary reaction. The term hazard does not include the lower voltage that causes annoyance, a stinging sensation, or mild heating of the skin. The Naval Ships Engineering Center has prescribed that an open circuit RFR voltage exceeding 140 volts on an object in an RFR radiation field be considered hazardous.

A common source of potential RFR burns is crane hooks. Transmitting antennas can induce RFR voltages in nearby crane structures and wire ropes. Figure 3-3 shows areas on a crane in which inductive and capacitive charges may be induced by RFR. Some crane/antenna problems can be eliminated by relocating the associated antennas, but each installation requires special considerations. The locations of ship's antennas are based on the desired radiation patterns, taking into account the physical limitations imposed by the ship's structure. Often, the relocation of antennas, although physically permissible, is not feasible because of the location of the associated transmitters.

RFR voltages measured aboard ships show that resonance effects may occur at frequencies between 2

Figure 3-3.-Electrical equivalent of cargo handling equipment.

and 30 Mhz. The careful use of frequency can reduce the coupling of RFR voltages induced in crane structures and rigging. A better approach, however, is the use of RFR high voltage insulator links, which provide protection for personnel against RFR burns. (Refer to Link RFR High Voltage Insulator for Ship Cranes, MIL-L-24410 (SHIPS)). Two separate bands of fiberglass filament wound on two zinc-coated steel saddles provide the required high electrical resistance, low capacitance, high tensile strength, ruggedness and fail-safe features of the insulator links. While the inner band normally carries the full working load, the outer band can carry the full working load if the inner band breaks.

When proper precautions are taken, personnel handling rigging will not be harmed as long as nearby electronic transmitting equipment is operated at an output of 250 watts or less, average (at any frequency). HOWEVER, PERSONNEL SHOULD BE CONSTANTLY ALERT TO THE FACT THAT EVEN UNDER THE ABOVE OPERATIONAL LIMITS, ELECTRONIC TRANSMITTING EQUIPMENT CAN CAUSE HAZARDOUS VOLTAGES TO BE INDUCED IN THE STANDING RIGGING AND OTHER PORTIONS OF A SHIP'S STRUCTURE, PARTICULARLY STRUCTURES AND OBJECTS (i.e., AIRPLANES

AND HELICOPTERS) THAT PROTRUDE FROM THE SHIP IN THE SAME PLANE AS THE RADIATING SOURCE. The RFR voltage induced in a ship's structures, rigging, or other objects will cause burns to personnel when they contact conductive objects. The burn hazard problem, its causes, and remedial techniques are discussed in chapter 3 ("RFR Burns") of Electromagnetic Radiation Hazards (U) (Hazards to Personnel, Fuel and Other Flammable Material) (U), NAVSEA OP 3565/NAVAIR 16-1-529/ NAVELEX 0967-LP-624- 6010/Volume I.

Q1. What do the letters RFR stand for when associated with radiation safety?

Q2. What are the three categories of electromagnetic radiation hazards?

Q3. What are the three classifications of ordnance susceptible to RFR?

Q4. What NAVSEA publication specifies safe distances from radiation sources for fueling? Q5. If you confirm that someone has been overexposed to RFR, what instruction must you use to properly report the incident?

Q6. According to the Naval Ships Engineering Center, what is the minimum RFR voltage in an open circuit that qualifies as hazardous?