If the vapor density of the released agent is greater than the vapor density of air, the cloud will pancake, sink, and cling to the surface of the earth. Generally, during the first 30 seconds, the cloud growth will be independent of ambient meteorological conditions, although the rate of dosage buildup is affected by the existing weather. The chemical cloud then will be subjected to forces which act to tear it apart and dilute its concentration. The heavier the agent, the longer the cloud will retain its integrity. An aerosol can be either a liquid or a solid substance consisting of finely divided particles suspended in the atmosphere.
Airborne aerosols behave in much the same manner as vaporized agents.
Aerosol clouds are heavier than vapor clouds, and they tend to retain their form and settle back to earth. Being heavier than vapor clouds, they are affected to a lesser extent by turbulence. Evaporation of liquid agent will cause the agent to form into vapor. Depending upon volatility, the clouds are usually of low concentration, have about the same temperature as the surrounding air, and tend to remain near the surface because of high vapor density. The evaporated agent cloud will behave in the same fashion as a vaporized chemical agent cloud except, being many times heavier, is less affected by turbulence and tends to follow terrain contours.