There are six RFR radiation hazard (RADHAZ) warning signs (fig.3-8). Requisitioning information is provided on the signs themselves. Consult with your leading petty officer (LPO) to obtain the appropriate signs if they are not posted in your workspace.

RADHAZ signs are made of anodized aluminum and come in two authorized sizes: large (14-inches by 14-inches) and small (5-inches by 5-inches). The large signs are reserved for shore use. The small signs may be used either aboard ship or ashore.

Figure 3-7.-Stack gas warning sign.

The signs shown in figure 3-8 were approved for use in 1990. Some old style signs may still be posted in various work areas. If you find older style RADHAZ signs posted in an area, you do not have to replace them with the new style signs unless they are damaged or illegible.

The purpose of each type of RADHAZ sign is explained below.

Type 1-"WARNING RADIO FREQUENCY HAZARD ... KEEP MOVING"

The type 1 sign advises personnel not to linger in an area surrounding HF antennas where RFR permissible exposure limit (PEL) can be exceeded. There is no danger from exposure to HF radiation in these areas for short periods. However, no one should remain within the area (defined by a 4-inch red line/circle on the deck) longer than 3 minutes within a 6 minute period.

When type 1 signs are required, install them at eye level, or where they can be seen easily, outside the PEL boundary.

Type 2-"WARNING RADIO FREQUENCY HAZARD ... BEYOND THIS POINT"

The type 2 sign is used to keep personnel from proceeding past a designated point unless they comply with established RADHAZ avoidance procedures. These procedures are discussed in ship's doctrine, such as the "MAN ALOFT BILL." You will probably not find deck markings in these areas.

Type 2 signs are installed at eye level at the bottom of vertical ladders or suspended at waist level between the handrails of inclined ladders. When type 2 signs are used as temporary barriers, such as when weapons direction radars are radiating, they are installed at waist level on a nonmetallic line.

Type 3-"WARNING RADIO FREQUENCY HAZARD ... BURN HAZARD"

The type 3 sign advises personnel to use special handling procedures when they touch a designated metallic object, or simply to not touch it. This object is an RFR burn source when it is illuminated by energy from a nearby transmitting antenna. Although the hazard may exist only at certain frequencies or power levels, personnel should regard the object as a hazard unless the transmitter is secured.

Figure 3-8.-Sample RADHAZ signs.

NOTE: Whenever possible, the RFR burn source should be replaced with a nonmetallic substitute or relocated or reoriented to eliminate the hazard before resorting to a type 3 sign for personnel protection.

A type 3 sign should be installed on the RFR burn source or in the immediate vicinity where it can be seen easily. When used on cargo handling running rigging, type 3 signs should be mounted on the hook insulator. Personnel should be warned to not touch the wire/rigging above the insulator. More than one type 3 sign should be installed on larger burn sources that can be approached from multiple directions.

Type 4-"WARNING RADIO FREQUENCY HAZARD ... FUELING OPERATIONS"

The type 4 sign advises of the hazards of electromagnetic radiation to fuels (HERF). These signs are normally used only on ships that carry aviation gasoline (AVGAS) or automotive gasoline (MOGAS). Marine diesel fuel and JP-5 jet fuel are not considered to have a HERF problem and require no special electromagnetic safety precautions during fueling. Most naval ships do not carry gasoline. An exception to this is amphibious ships carrying gasoline-powered landing vehicles. Aboard ships that carry AVGAS or MOGAS, personnel should observe the following precautions during fueling or fuel transfer operations:

1. Secure all transmitting antennas located within the quadrant of the ship in which fueling is being conducted.

2. Ensure that RADHAZ cutouts for microwave radiators are not overridden during fueling, which could result in the illumination of the fueling areas.

3. Do not energize any radar or communications transmitter on any aircraft or vehicle.

4. Do not make or break any electrical, static ground wire, or tie down connection, or any metallic connection to the aircraft or motor vehicle while it is being fueled. Make the connections before the fueling commences. Break them afterward.

Type 5-"WARNING RADIO FREQUENCY HAZARD (SPECIAL CONDITION)"

The type 5 sign has a blank area for filling in special safety precautions. Its purpose is to advise personnel of procedures to follow when other

RADHAZ warning signs are not appropriate. Examples of directions that can be filled in on a type 5 sign include:

"Inform OOD before placing system in radiate."

"In manual mode, do not depress below horizon between and degrees relative."

"Ensure temporary exclusion barriers are in place before radiating."

"Do not stop antenna between and degrees while radiating."

A type 5 sign is normally installed below decks in a system operating room. It should be installed in the vicinity of controls such as a radiate switch or antenna control switch, where the person operating the gear in normal operation can see it. When mounted on system cabinets or control panels, RADHAZ signs should not obscure switch labels, meters, indicators or nameplate data.

Type 6-"WARNING RADIO FREQUENCY HAZARD ... HAZARD TO ORDNANCE"

The type 6 sign advises of hazards of electromagnetic radiation to ordnance (HERO). NAVSEA OP 3565 explains the purpose of HERO signs and where to place them.

ROTATION HAZARD WARNING

Rotating directors present a serious danger to personnel near them. To guard against this hazard, be sure the topside area near the directors is cleared of all personnel before you energize a director. "DANGER ROTATION HAZARD" warnings should also be posted or painted in conspicuous places to alert unwary personnel.

Q7. What OPNAV instruction gives the OOD guidance for the Working Aloft Check Sheet?

Q8. What size RADHAZ signs should be used on ships?

Q9. What type of RADHAZ warning signs should be used when other RADHAZ signs are NOT appropriate?