DHD is the Downwind Hazard Distance- the distance the contamination hazard
will travel dependent on the weapon type, method of delivery, terrain, and the
10 nautical miles.
Wind speed and direction, air temperature, mean daily surface temperature,
relative humidity, total cloud cover, air stability/air-sea temperature difference,
presence and type of precipitation, and the presence of temperature inversion
NBC 3 CHEM, chemical downwind message for ground forces and NAV NBC 3
CHEM, chemical downwind message for Naval Forces.
The hazard area (grid reference or geographical reference).
Type and case of chemical attack, maximum downwind hazard distance, and half
Unstable air, temperature 17°C. relative humidity of between 90% and 99%. rain
showers, and broken cloud cover.
In a circle, I kilometer (1/2 nautical mile) from ground zero for the attack area, and
10 kilometers from ground zero for the hazard area (ground forces) or 15 nautical
miles (Naval Forces).
The location of the attack, the Chemical Downwind Direction (CDD). the
Downwind Hazard Distance (DHD), and the Half Sector Angle (HSA).
In chemical spray attacks from aircraft when the hazard area will most likely be in
an elongated pattern.