In many types of public health emergencies, the safest thing to do is simply to stay indoors. If the air is unsafe because of hazardous chemicals, radiation, or a spray (aerosol) release of a biological agent, local authorities may advise you to "shelter in place," which limits your exposure to the outside air.

To shelter in place:

1. Make sure all family members and pets that are at home are inside. Then close and lock all doors and windows.
2. Turn off air conditioners, fans, and furnaces. Close vents and fireplace dampers.
3. Move to an inner room, preferably at or above ground level and without windows. (If the incident involves radiation, authorities may tell you to take shelter in a basement.) If you have an emergency supplies kit, take it with you. At the very least, make sure you have a battery-powered radio and plenty of drinking water.
4. If local authorities advise you to do so, use duct tape to secure plastic sheeting around door and window frames.
5. Stay tuned in to the local news, and stay inside until local authorities say that it is safe to come out.