Housing inspectors are often called to homes that are filled from top to bottom with an excessive number of belongings or an overabundance of animals. In some cases, the home is filled with both things and animals. The accumulations are often so great that it is impossible to walk in the home. This little understood phenomenon is referred to as "hoarding". The requests for inspections at these homes are most often received from the Police Department, Fire Department, concerned family members, landlords, or social service agencies.

Hoarding is the collecting of and failure to discard large numbers of things or animals until it interferes with day-to-day functions. Animal hoarding has the added symptom of the fact that there are such a large number of animals the hoarder cannot provide acceptable care. Hoarding often causes health and safety hazards. Huge piles of newspapers, clothes, and food serve as a harborage for rodents and insects and present a fire safety hazard to the occupant and the general public. Blocked egresses hinder entry by emergency responders and the ability of the occupant to exit in case of crisis. Floors can buckle from the weight and combustibles can ignite. In addition, the occupant is in danger of falling or of respiratory illness from problem indoor air quality. Hoarding of animals presents additional health risks from diseases transmitted by animals to humans and extreme air quality problems such as environmental ammonia.

Little is known of the causes of hoarding, but there is a great deal of research being done to more clearly define the phenomenon. Many experts believe it is a type of obsessive-compulsive disorder although it is seen in conjunction with a variety of illnesses and is therefore difficult to place in a diagnostic category. Although the reason is not understood, it is estimated that the elderly represent the majority of people who hoard.

For more information about animal hoarding, see The Hoarding of Animals Research Consortium or Mass Housing.