In a chemical and nuclear battlefield, there needs to be some way of indicating that certain areas are out of bounds to troops due to contamination on the ground. Whilst hazard tape is fine for defining the perimeter of an area, it doesn’t give troops an easily identifiable indication of what the hazard is. During the Cold War the NATO powers developed a consistent set of warning signs in the form of inverted triangles in different colours to indicate the different CBRN hazards:
These signs are in the form of a self adhesive sticker that can be affixed the boundary of an area. Three colours were used, white with black lettering for an area affected by nuclear radiation:
A yellow sign for areas affected by gas or other chemical agents:
And finally blue signs for biological agents. These examples are stickers which the original packaging warned woud not stick to wet concrete or brick. Other examples were produced in plastic to be hung on a piece of tape. The exact details of the forms these signs should take was carefully prescribed (here in a US Army publication, although the principles remained the same across NATO):
PART A – NBC CONTAMINATION MARKERS
Because of the potential effects posed by chemical or biological agents on personnel, markers have been devised to identify areas contaminated by these agents or areas which contain chemical mines. When a contaminated area has been identified, its boundaries are marked with contamination markers.
Signs used for marking contaminated areas are standard throughout North Atlantic Treaty Organization (NATO). A NATO marker is a right-angled isosceles triangle. The base is approximately 28 centimeters (11 1/2 inches) and the sides are 20 centimeters (8 inches). It has holes used for hanging. It may be placed on boundary fences, poles, trees, or rocks. Place a sign with the point of the triangle facing down.
The United States marks contaminated areas with the NBC Contamination Marking Set. It contains everything needed to mark an area – flags, ribbon, crayons, mounting stakes, and a carrying container. TM 3-9905-001-10 describes the kit and its use. A NATO NBC Marking Set is available and bears the stock number NSN 9905-12-124-5995. If units do not have the kit available, they can make the signs out of available metal, plastic, or wood. These field expedient signs must be of standard shapes, sizes, and colors.
Areas which are found to be contaminated with more than one type of contamination will be marked with markers of each type of contamination. The color and size permits easy identification. The color indicates the type of contamination. The primary or background color indicates the general hazard. The secondary color gives hazard specifics. Identified contaminated areas are marked unless they are to be abandoned to Threat Forces. Information concerning the contamination is printed on the front of the marker as shown in Figure 1-1.
When placing contamination markers in position, the markers should be placed at short intervals around the contaminated area. Markers should be prominently displayed on roads or paths leading into the contaminated area. Fluorescent paint used on the markers will make them more visible during hours of darkness.
Equipment evacuated from a contaminated area must be marked. The type of agent and current date and time should be posted on the markers with a marker placed on each side, the front, and rear of the equipment