WHAT CHEMICAL CONCENTRATION IS SAFE?
The Problem: A chemical spill has occurred or can potentially occur and a public evacuation is ordered. The evacuation is ordered because the chemical is toxic and is or may become airborne. Even if the chemical is a liquid and spills on the ground, the liquid will likely evaporate dispersing the chemical in the air. Explosions can occur releasing large quantities of the chemical at once. Anyone downwind of the release can inhale the chemical. A decision must be made on the evacuation distance, or whether in some situations people may remain inside buildings with windows closed until the danger has passed. There are practical limits of how many people can be evacuated and the evacuation distance. Obviously some people will or can potentially be exposed to the chemical in the air. What concentration in the air might be considered safe? This is not an easy question to answer. Some chemicals are dangerous because when inhaled they interfere with the body metabolism. Some irritate the eyes
