A nuisance per se, or at law, is an act, occupation, or structure that is a nuisance at all times and under any circumstances, regardless of location or surroundings. It typically infringes upon public rights and interests. Conversely, a nuisance per accidens, or in fact, arises from the manner in which the activity or property use is conducted in relation to its surroundings. It’s deemed a nuisance due to its impact on specific individuals rather than the general public.
For example: A factory that emits harmful pollutants directly into residential areas could be deemed a nuisance per accidens if it significantly impairs local residents’ health and enjoyment of their properties, despite the factory’s operations being legal and ordinarily permissible in an industrial zone.