An ultrahazardous activity in the common law of torts is one that is so inherently dangerous that a person engaged in such an activity can be held strictly liable for injuries caused to another person, even if the person engaged in the activity took every reasonable precaution to prevent others from being injured. In the Restatement of the Law 2d, Torts 2d, the term has been abandoned in favor of the phrase "inherently dangerous activity."
There are several categories of activities which are commonly recognized as being ultrahazardous, and therefore subject those who engage in them to strict liability. These include:
Transportation, storage, and use of dynamite and other explosives
Transportation, storage, and use of radioactive materials
Transportation, storage, and use of certain hazardous chemicals
Keeping of wild animals (i.e. animals that are not normally domesticated in that area)
Note that in this context domesticated does not merely refer to animals that are commonly bred and raised in captivity, such as alligators.
Keeping of domesticated animals that have a known propensity for dangerous behavior (e.g., keeping a dog that has attacked people before)
A person who is injured by one of these ultrahazardous activities while trespassing on the property of the person engaged in the activity is barred from suing under a strict liability theory. Instead, they must prove that the property owner was negligent.
