"Depending on the nature and timing of a catastrophe, emergency managers may warn people of whether it is safer to evacuate or to shelter in place. In an evacuation, people leave their homes and businesses and travel to a safe location away from danger. In some instances, it is safer for people to quickly seek shelter indoors-in homes, schools, businesses, or public buildings-than to try to travel. Shelter-in-place would be used when there is little time to react to an incident and it would be more dangerous to be outside trying to evacuate than to stay indoors for a short period of time. Additional protective actions that the emergency managers may recommend would include turning off air conditioners and ventilation systems and closing all windows and doors. Sheltering-in-place might be used, for example, in the event of a chemical accident. FEMA recommends people have food, water, and medical supplies and be prepared to stay indoors for at least three days". (DOT, Catastrophic Hurricane Evacuation Plan Evaluation: Report to Congress, June 1, 2006, p. 2-2)