An emergency is an urgent, unexpected, and usually dangerous situation that poses an immediate risk to health, life, property, or environment and requires immediate action. Most emergencies require urgent intervention to prevent a worsening of the situation, although in some situations, mitigation may not be possible and agencies may only be able to offer palliative care for the aftermath.
While some emergencies are self-evident (such as a natural disaster that threatens many lives), many smaller incidents require that an observer (or affected party) decide whether it qualifies as an emergency.
The precise definition of an emergency, the agencies involved and the procedures used, vary by jurisdiction, and this is usually set by the government, whose agencies (emergency services) are responsible for emergency planning and management.
An incident, to be an emergency, conforms to one or more of the following, if it:
Poses an immediate threat to life, health, property, or environment
Has already caused loss of life, health detriments, property damage, or environmental damage
has a high probability of escalating to cause immediate danger to life, health, property, or environment
In the United States, most states mandate that a notice be printed in each telephone book that requires that someone must relinquish use of a phone line, if a person requests the use of a telephone line (such as a party line) to report an emergency. State statutes typically define an emergency as, "...a condition where life, health, or property is in jeopardy, and the prompt summoning of aid is essential."
Whilst most emergency services agree on protecting human health, life and property, the environmental impacts are not considered sufficiently important by some agencies. This also extends to areas such as animal welfare, where some emergency organizations cover this element through the "property" definition, where animals owned by a person are threatened (although this does not cover wild animals).