When floodwater enters the
living area of a building, water, organic material, and bacteria
and other microorganisms are deposited onto hard surfaces and
into porous building materials and furnishings. Many building
materials and furnishings that remain wet for more than 48 hours
will develop visible fungal colonies. These colonies are
commonly referred to as mold or mildew.
If a flooded building is to be
safely reoccupied, water and the deposited material must be
removed from the building and from building materials and
furnishings. In addition, all indoor fungal growth that occurred
as a result of flooding must be removed from the building by
cleaning. The use of biocides is recommended as the final step
in cleaning but is not adequate in the absence of thorough
cleaning.
Indoor biological contaminants
resulting from flooding of buildings can create significant
health risk for occupants. Unintentional ingestion of floodwater
or sediment can cause gastrointestinal diseases. Inhalation
exposure to airborne fungal spores or hyphae may cause
allergy-mediated symptoms including upper respiratory
irritation, bronchial irritation, asthma attacks, and
hypersensitivity pneumonitis. Some fungi may cause infectious
respiratory disease (e.g., aspergillosis), while others (e.g.,
Stachybotros sp.) generate toxins that may cause illness.
Chemical contamination of
buildings may result when containers in the flooded building are
spilled or when floodwater carries contaminants into the
building. In most cases, cleaning to remove floodwater, sediment
and debris will remove chemical contamination. If there is
reason to believe that there is significant chemical
contamination and that building occupants may be at risk, those
situations should be evaluated case by case.
In order to minimize exposure
to biological contamination in buildings and to reduce the risk
of illness or disease, these guidelines are offered for
re-occupancy of flooded buildings. A building should be
considered unsafe for occupancy until:
- Floodwater has been removed
and dried from all building materials; furnishings; and
heating, ventilating and air conditioning (HVAC) system
components.
- All building materials,
furnishings and HVAC system components have been dried so that
they will not support fungal growth.
- All sediment, debris and
organic material deposited by floodwater have been removed
from the building.
Any fungal growth on building
materials, furnishings, or HVAC system components that resulted
from flooding has been removed by thorough cleaning and not by
the application of biocides alone. The most direct means of
identifying fungal growth is by visual inspection. Air or bulk
cultured sampling is not usually necessary, particularly if
visible fungal growth is present.
These guidelines apply to the
parts of the building that are habitable (the heated living
area), the wall cavities, and chases adjacent to living areas.
Crawl spaces and unheated basements may not need to meet these
guidelines.
