shall be airtight when operating at internal static pressure not less than
500 Pa 2 inches water gage. Conform with noise reduction requirements
specified in paragraph entitled "Net Noise Reduction Values."
2.4
FLEXIBLE DUCTS AND CONNECTORS
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NOTE: Care should be taken not to locate flexible
ductwork in prisoner housing areas, areas accessible
to prisoners, or areas with concrete, gypsum board
or plaster ceilings.
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UL 181, Class I, UL listed, and additional requirements herein specified.
Provide to connect between rigid ducts and outlets or terminals. There
shall be no erosion, delamination, loose fibers, or odors from the ducts
into the air stream. At 120 degrees C 250 degrees F, minimum rating
pressures shall be [1500 Pa positive and 125 Pa negative, up to 20 meters
per second][6 inches water positive and 1/2 inch negative, up to 4,000 fpm]
[_____] [and] [500 Pa positive and 125 Pa negative, up to 13 meters per
second] [2 inches water positive and 1/2 inch negative, up to 2500 fpm]
[_____]. Flexible ducts shall be maximum [1] [2] [2 1/2] meters [4] [6]
[8] feet in length. Minimum bend radius shall be twice the duct diameter.
2.4.1
Materials
Interlocking spiral or helically corrugated type constructed of
[zinc-coated steel,] [corrosion-resistant steel], [aluminum,] [or]
[noncollapsible fire-retardant, chloroprene or chlorosulfonated
polyethylene impregnated, minimum one kilogram per square meter 30 ounces
per square yard] woven mineral fabric.
2.4.2
Insulation and Vapor Barrier
ASTM C 553 Type 1, Class B-2, minimum 25 mm one inch nominal thickness and
12 kilogram per cubic meter three-quarter lb./cu. ft.density. Sheathe
insulation with a vapor barrier having a maximum water vapor permeance of
0.20 perm in accordance with ASTM E 96, Procedure A. Coat ends of
insulation with cement to prevent erosion and delamination.
2.4.3
Joints
Make airtight slip joints, seal with pressure-sensitive vapor-seal adhesive
tape or duct sealer, and secure with sheet metal screws. To prevent
insulation compression, place 50 mm wide by 25 mm thick 2 inch wide by one
inch thick closed cell foam plastic spacers over joints under vapor
barriers. To provide a vaportight joint, provide a [zinc-coated steel]
[corrosion-resistant steel] [or] [aluminum] clamp over such spacers.
2.5
CASINGS AND PLENUMS
Factory fabricated components with field installation. Furnish certified
testing data from plenum or casing manufacturer obtainable directly from an
independent acoustical laboratory, listing sound absorption and
transmission loss characteristics of panel assembly. Sound absorption
coefficients and sound transmission loss, determined by an independent
laboratory, shall be in accordance with ASTM C 423 and ASTM E 90
respectively.
SECTION 15810N
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