FEMA 453 Design Guidance for Shelters and Safe Rooms

Table 2-1: UL 752 Ratings of Bullet-resisting Materials
Rating Ammunition Grain Minimum Velocity (fps)
Level 1 9 mm full metal copper jacket with lead core 2 , 8
Level 2 . Magnum jacketed lead soft point 8 ,2 0
Level 3 . Magnum lead semi-wadcutter gas checked 2 0 , 0
Level 4 . 0 caliber rifle lead core soft point 80 2, 0
Level 5
. 2 mm rifle lead core full metal copper jacket,
military ball
0 2, 0
Level 6 9 mm full metal copper jacket with lead core 2 , 00
Level 7
Level 8
ul = underwriters laboratories
. mm rifle full metal copper jacket with lead
core
. 2 mm rifle lead core full metal copper jacket,
military ball
Forced entry resistance is measured in the time it takes for an aggressor
to penetrate the enclosure using a variety of hand tools
and weapons. The required delay time is based on the probability
of detecting the aggressors and the probability of a response force
arriving within a specified amount of time. The different layers
of defense create a succeeding number of security layers that are
more difficult to penetrate, provide additional warning and response
time, and allow building occupants to move into defensive
positions or designated safe haven protection (see Figure 2-10).
The rated delay time for each component comprising a defense
layer (walls, doors, windows, roofs, floors, ceilings, and utility
openings) must be known in order to determine the effective
delay time for the safe room. Conventional construction offers
little resistance to most forced entry threat severity levels and the
rating of different forced entry-resistant materials is based on standardized
testing under laboratory conditions.
2- 8 Structural deSign criteria
,080
0 2, 0