Effective protection in the event of an accident or response depends on:
- the nature of the incident (is it an air or a water release?);
- the hazardous substances involved;
- the potential severity of the incident;
- the incident’s potential off-site effects;
- the quantity and type of the hazardous substance(s) involved;
- the treatment facilities available for emergency response.
Notification from the hazardous facility should trigger the implementation of the off-site emergency response plan, beginning with an initial assessment of the situation leading to a decision on which response actions are required.
In the case of the release of a toxic substance, the decision on whether the potentially affected community should shelter indoors or be evacuated should be taken by the responsible person designated in the emergency plan. The decision made should be based on likely exposure and possible health effects.
Emergency warning alert systems should be available to warn the potentially affected public that an accident has occurred or that there is an imminent threat of an accident:
- The system chosen may vary depending on local culture and conditions, providing that it is effective and timely. Suitable warning systems could include, for example, sirens, automatic telephone messages, mobile public address systems or a combination of systems.
- The potentially affected community should be notified of the systems which will be used in an emergency, and the systems should be tested in advance.
Emergency warning alert signals and announcements should be fully understood by the public and the public should know how to respond appropriately in an emergency. Time and distance from the contamination source are important factors in limiting exposure to the public. The shorter the period of time an individual stays in a contaminated area and greater the distance from the source of contamination, the smaller the exposure received by them.