As of 2015, the American Red Cross' "Find Open Shelters" online search function can help you find an emergency shelter quickly. The National Shelter System updates this database every 30 minutes. During an emergency, use the site's "Safe and Well" function to register your location or check on the well-being of a family member.
Some circumstances, such as a chemical spill, may require you to "shelter-in-place." This usually means you should stay inside your home until instructed otherwise. In some cases, however, you may receive instructions to stay inside one room and seal it from outside airflow. For this scenario, choose a room with a bathroom or other water supply, seal it, and stay inside with emergency food and water supplies.
If possible, prepare emergency supplies before a disaster strikes. You should have 1 gallon of water per person per day, non-perishable food and a can opener. Stock a flashlight, a handcrank- or battery-operated radio, first aid kit and a seven-day supply of any medication. Tailor the supplies of your emergency kit to fit the needs of your household, especially if it includes an elderly person or an infant. Include at least a three-day supply of food and water for your pets, if necessary.