STACK GAS WARNING SIGN
A warning sign to alert personnel working aloft
near smoke pipe (stack) gases is shown in figure 3-7.
One sign should be mounted near the bottom of each
access ladder leading aloft. Another sign should be
located at the top of each ladder but mounted on the
base of the antenna pedestal.
RFR HAZARD WARNING SIGNS
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.
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
The purpose of each type of RADHAZ sign is
Type 1WARNING 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
When type 1 signs are required, install them at eye
level, or where they can be seen easily, outside the PEL
Type 2WARNING 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 ships 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 3WARNING 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 3-6.High voltage warning sign.
PERSONNEL ARE CAUTIONED TO GUARD
AGAINST POISONOUS EFFECTS OF SMOKE PIPE
GASES WHILE SERVICING EQUIPMENT ALOFT.
WHEN SERVICING EQUIPMENT IN THE WAY
OF SMOKE PIPE GASES USE OXYGEN BREATHING
APPARATUS AND A TELEPHONE CHEST OR
THROAT MICROPHONE SET FOR COMMUNICATION
WITH OTHERS IN WORKING PARTY.
OBTAIN NECESSARY EQUIPMENT BEFORE
Figure 3-7.Stack gas warning sign.