Emergency alert radios, or weather radios, are the best source for indoor warnings. These radios emit a loud alert signal, and then a voice message is given when a watch/warning has been issued for the area. Every home, office, church, business or any area where people gather should have an emergency alert radio. They can be used to give warning of many types of emergencies, including a chemical emergency, through the cooperation of the National Weather Service.
Sirens are outdoor warning devices. They are not intended to be heard indoors. Sirens may be used for weather warnings, chemical accidents, and other hazards. If you hear a siren, you should monitor area radio or TV stations or your emergency alert radio for details and then activate your Emergency Preparedness Plan
according to the type of emergency.