Exposure B
Urban and suburban areas, wooded areas, or other terrain with numerous closely
spaced obstructions having the size of single-family dwellings or larger.
Use of this exposure category shall be limited to those areas for which
terrain representative of exposure B prevails in the upwind direction for
a distance of at least 1,500 feet (460 m) or 10 times the height of the
building or structure, whichever is greater.
Exposure C
Open Terrain with scattered obstructions having heights generally less than
30 feet (9.1 m). This category includes flat open country and grasslands.
Exposure D
Flat, unobstructed areas exposed to wind flowing over water for a distance
of at least 1 mile (1.61 km). This exposure shall apply only to those building
and other structures exposed to the wind coming from over the water. Exposure
D extends inland from the shoreline a distance of 1,500 feet (460 m) or
10 times the height of the building or structure, whichever is greater.
Category 1
Buildings and other structures that represent a low hazard to human life
in the event of failure including, but not limited to:
* Agricultural facilities
* Certain temporary facilities
* Minor storage facilities
Category 2
All buildings and other structure except those listed in Categories 1, 3,
and 4.
Category 3
Buildings and other structures that represent a substantial hazard to human
life in the event of failure including, but not limited to:
* Buildings and other structures where more than 300 people congregate
in one area
* Buildings and other structures with elementary school, secondary school,
or day-care facilities with capacity greater than 250
* Buildings and other structures with a capacity than 500 for colleges or adult
education facilities
* Healthcare facilities with a capacity of 50 or more resident patients but
not having surgery or emergency treatment facilities
* Jails and detention facilities
* Power generating stations and other public utility facilities not included
in category 4
* Buildings and other structures containing sufficient quantities of toxix
or explosive substances to be dangerous to the public if released
Category 4
Buildings and other structures designated as essential facilities including,
but not limited to:
* Hospitals and other healthcare facilities having surgery or emergency
treatment facilities.
* Fire, rescue and police stations and emergency vehicle garages
* Designated earthquake, hurricane, or other emergency shelters
* Communications centers and other facilities required for emergency response
* Power generating stations and other public utility facilities required in
an emergency
* Buildings and other structures having critical national defense functions