ETL 1110-3-456
16 Aug 94
f. Doors. Metal doors, especially large metal overhead
doors or roll-up doors are large radar reflectors and open doors
produce a large radar signature similar to that of windows.
g. Exhaust Vents. Exhaust vents create a signature that is
easily seen by thermal infrared viewing. The signature is
created by pipes, louvers, and other surfaces that are heated by
the exhaust. The hot exhaust gases are not easily detected.
h. Cooling Towers. The use of cooling towers should be
avoided because under some atmospheric conditions they create
condensation clouds that can be seen from large distances.
7. CAMOUFLAGE AND CONCEALMENT MEASURES. General camouflage and
concealment measures to be considered in the design of facilities
with manned attack aircraft threats are discussed below. These
measures generally consist of reducing conspicuousness or orient-
ing conspicuous features away from the most likely attack avenues
or toward natural obstructions such as mountain ridges, hills, or
tall trees to avoid direct line-of-sight viewing by attack
aircraft.
a. Site Preparation. Clearing and grading of natural vege-
tation should be kept to a minimum. When facilities are con-
structed in forested areas, as much of the original foliage as
possible should be left in place. If large forested areas must
be cleared, reforestation should take place as soon as possible
to replace the natural foliage.
b. Blending With Surroundings. If possible, the facility
should blend with the surroundings so that it is hard to tell
from the air where the facility begins and ends. This can mean
blending with adjacent terrain or imitating or joining adjacent
buildings. Samples of blending site terrain features are shown
in figures A-7 and A-8. A sample of blending a partially buried
facility with surrounding topography and foliage is shown in
figure A-9. Avoid the use of uniform surfacing materials such as
bare ground, paving, and grass that contrast with the structure.
When the close proximity of existing facilities prevents blending
with the terrain, use the same architecture as the nearby facili-
ties; e.g., use the same color, patterns, and roof style.
c. Soil and Foliage Cover. Soil and foliage are among the
most effective cover treatments because they reduce the effec-
tiveness of all viewing; i.e., visual, infrared, and radar.
However, these cover treatments can still make a facility con-
spicuous when the nearby surroundings are not considered. For
example, an isolated group of trees can be conspicuous when
placed in the middle of several buildings.
A-12
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