Public warnings are urgent communications issued from time to time by various entities in an attempt to reduce preventable injuries or deaths. The following principles are proposed as the basis of a professional standard of public warning practice:
1. When should a public warning be issued?
1.1. A warning should be issued whenever there is an imminent threat to life or health
of which an individual or community may be unaware. “Imminent” means that more routine means of communication would not be effective.
1.2. Generally, a warning should be issued as soon as an appropriate recommendation for protective action can be made. It is preferable to issue a preliminary warning message and then refine it later rather than to wait for perfect information that may arrive too late.
1.3. In situations where a delay is unlikely to substantially affect the outcome for people at risk, consideration may be given to delaying warnings during overnight hours (e.g., from 10 PM until 6 AM) or while the recommended protective action might conflict with immediate response activity.
1.4. A fear of public panic is NOT a sufficient reason for delaying a public warning. Panic results when social bonds are torn by an acute sense of individual competition for limited opportunities of escape from a dire threat. It rarely occurs as the result of a public warning. Timely warning with clear protective action recommendations can actually reduce the potential for panic.
1.5. By their nature public warnings can never be guaranteed to be timely, effective or accurate; the issuance of a public warning is a voluntary and discretionary act.
2. By whom should a public warning be issued?
2.1. A public warning may be issued by any individual or entity that is aware of an imminent threat to human life or health, particularly if that individual or entity believes that some or all of the target audience will not receive warning from another source.
2.2. A public warning is best issued by an individual or entity that is familiar to, and with, the receiving audience.
2.3. A public warning is best issued by an individual or entity with the capacity and authority to coordinate warning information and response activity among all the responsible actors (e.g., an Incident Commander or a senior elected official.)
3. To whom should a public warning be issued?
3.1. A public warning should be given to all individuals whose life or health is at risk.
3.2. A public warning may also be shared with individuals and agencies that may be able to provide necessary assistance to individuals at risk.
3.3. To the extent possible public warnings should NOT be distributed to individuals who are neither affected by nor in a position to provide assistance with a hazard.
4. What should be the content of a public warning?
4.1. A public warning message should indicate as specifically and precisely as possible which persons are at risk from a particular hazard, in terms of their location or some other distinguishing characteristic. In some cases it may also be useful to identify individuals or communities that are explicitly NOT at risk from that hazard.
4.2. A public warning message should describe the nature of the hazard in plain terms that are understandable by the target audience. If an emergency response to the hazard is planned or underway, that activity should be described as well.
4.3. A public warning message should describe one or more protective actions that individuals or groups can take on their own to improve the outcomes for themselves and their neighbors. Where more than one protective action is suggested, criteria should be offered by which individual recipients can select the best course for themselves.
4.4. A public warning message should provide information on when the hazard is expected to materialize (which may be “currently”) and, if possible, should include a forecast of how long the hazard will persist.
4.5. When possible a public warning message should provide recipients with an expectation of what is likely to happen next. In some cases this will simply be an estimate of when and how they will receive additional information.
5. How should public warnings be disseminated?
5.1. Whenever possible, public warnings should be transmitted to the public by multiple media simultaneously. Using more than one means of delivery increases audience reach and improves technical reliability, and also enhances warning effectiveness by confirming and reinforcing the warning message.
5.2. Delivery media for a particular warning should be chosen with an eye to balancing the need for wide and immediate attention with the need not to desensitize unaffected audiences with irrelevant warnings.
5.3. Wherever possible, warning message recipients should be encouraged to share the warning message with friends and neighbors, particularly those who may be isolated by physical or sensory disability, language ability or other factors.
5.4. Wherever possible, warning messages should be delivered in multiple formats to accommodate the special needs of recipients with physical or sensory disabilities, or who do not speak a particular language. However, delays in the conversion of a warning into multiple forms are NOT a valid reason for delaying release of a public warning in whatever form is most rapidly achievable.
6. How should uncertainty be expressed in public warnings?
6.1. Where facts surrounding a warning situation are uncertain, that uncertainty should be disclosed frankly in the warning message.
6.2. To avoid creating a false sense of precision, uncertainties and probabilities should be expressed in general, non-numeric terms (e.g., “observed” / “likely” / “possible” / “unlikely”) instead of percentages or other precise-sounding language.
6.3. Descriptions of uncertainty should address not only any uncertainty about the hazard itself, but also any uncertainty about its effects on the at-risk population.
6.4. Uncertainty is NOT a valid reason for delaying a public warning. It is preferable to cancel or amend a warning as better information becomes available than to risk preventable injuries or deaths by delaying the initial warning message.