PLOTTING CHEMICAL CONTAMINATION DATA

PLOTTING CHEMICAL CONTAMINATION DATA Plotting chemical contamination areas is easy once you understand the terms and the contents of a chemical downwind message. Normally. the military grid squares contaminated by a chemical weapon are provided in element PAPA-ALFA of the chemical downwind message. In a NAV NBC 3 CHEM message, the contaminated area boundary positions should be provided in degrees, minutes, and seconds (DMS). A better picture of the contaminated area is constructed using other parameters contained in the message. From the NAV NBC 3 CHEM message, check element ZULU-BRAVO to determine the type and case of the attack. Element ZULU-ALFA contains environmental information, and, on occasion, plain language may be used in lieu of the meteorological reporting code. Now let’s discuss the methods used to plot initial contamination for circular, triangular, and double- triangular hazard areas. Circular Hazard Area When winds are 5 knots or less in a type A-case (a) or a type B-case (a), case (b), or case (c) attack, the attack area is plotted as a circular hazard area. The important factor is that the prevailing wind speed is 5 knots or less. In both type A-case (a) and type B-case (a) attacks, the attack area is drawn as a 1/2-nautical-mile- radius (1-kilometer-radius) circle around the location where the chemical agent was deployed. In a type B- case (b.) attack, the attack area is drawn as a 1/2- to 1- nautical-mile-radius circle centered on the attack site and in a type B-case (c), the attack area is drawn larger than a 1-nautical-mile radius, depending on the type of attack. In all of these situations, the hazard area is a 10- kilometer-radius circle around the attack area for Figure 5-11.—Circular hazard area. Plotted type B-case (a) chemical attack, land. Wind speed 10 KPH/5 kt or less. 5-14