Also known as: inherently dangerous activities · ultrahazardous activity · abnormally dangerous activity
Written by attorneys · grounded in primary & secondary sources — see below
An activity that can be carried out only by the exercise of special skill and care and that involves a grave risk of serious harm if done unskillfully or carelessly. The activity triggers strict liability rules that limit certain defenses such as contributory negligence and that extend liability for resulting intrusions onto land even when the entry itself is unintentional.
Imani Idowu hired Imperial Motors to transport volatile chemicals by rail through a populated area. A derailment released fumes onto adjacent property owned by Isaiah Ishikawa. Ishikawa had ignored posted warnings and remained outside during the known transport window. Because the activity qualifies as inherently dangerous, Ishikawa's decision to stay outside does not bar recovery under strict liability principles.
Insight Consulting conducted pressure testing on chemical tanks near the boundary with Ingrid Innes's fabrication shop. An uninspected relief valve failed and released corrosive vapor that drifted onto Innes's yard, pitting equipment. The testing operation created the risk of harmful entry even without an intentional crossing, so Insight faces liability for the resulting damage.
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Ira Irving operated a combine harvester along the shared line with Isabelle Inman's organic field. An undetectable internal brake defect caused the machine to roll a few feet across the boundary and flatten kale. Because the operation was neither an inherently dangerous activity nor conducted negligently, Irving avoids liability for the unintentional entry.
American Cyanamid arranged shipment of acrylonitrile by rail through a dense urban corridor. A spill occurred at a switching yard operated by Indiana Harbor Belt. The carrier sought contribution from the shipper under strict liability theories tied to the hazardous nature of the cargo movement.
Omega Flex supplied flexible gas piping later installed in a residence. A lightning strike caused the piping to fail and release gas that exploded. The buyer sued the manufacturer, arguing that the product's installation and use involved risks that could not be eliminated by ordinary care.
Consolidated Rail operated a rail yard where a tank car caught fire. Municipal authorities evacuated a one-mile radius that included People Express Airlines' terminal, forcing cancellation of flights. The airline sought recovery for business losses caused by the evacuation triggered by the hazardous cargo incident.
Contributory negligence does not bar recovery against the party carrying on an inherently dangerous activity. The rule preserves strict liability even when the plaintiff acted carelessly, unless the plaintiff voluntarily and unreasonably assumed the specific risk.
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An activity qualifies when it creates a high probability of serious harm that cannot be eliminated by reasonable care. Negligent or reckless conduct during such an activity that causes a thing to enter another's land supports liability if the entry produces actual harm to protected interests.
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An unintentional and non-negligent entry does not trigger liability when the actor is not engaged in an inherently dangerous activity. The exception removes the usual protection for accidental entries once the activity itself carries inherent danger.
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A principal remains liable for harm caused by an independent contractor's negligence when the work itself is inherently dangerous. The exception prevents the principal from shifting responsibility for risks that require special precautions regardless of who performs the work.
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…The other count asserts that the transportation of acrylonitrile in bulk through the Chicago metropolitan area is an abnormally dangerous activity, for the consequences of which the shipper (Cyanamid) is strictly liable to the switching line, which bore the financial brunt of those consequences because of the decontamination measures…