ETL 1110-3-485
15 Oct 97
3.4 Fire Area Limitations. Helicopter hangar bay areas will not exceed 5576 m2 (60,000 ft2).
Where larger areas are required, fire walls having a minimum 3-hour resistance rating will be
provided to limit hangar bay fire areas.
3.5 Internal Fire Separations. Walls and ceilings separating helicopter hangar bays from
attached, adjoining or contiguous shops, offices, parts storage or similar areas, will have at least
1-hour fire resistive rating with openings protected by listed or approved fire doors having a
minimum fire resistance rating of 45 minutes.
3.6 Roofs. Roof coverings will be listed as Class "A" or "B" when tested in accordance with
NFPA 256, Standard Methods of Fire Tests of Roof Coverings. Where insulated metal deck
assemblies are used, such will be equivalent to Factory Mutual Class I.
3.7 Structural Steel Columns. Protection of exposed steel columns is not required.
3.8 Draft Curtains. Draft curtains will be provided to form roof pockets with individual areas
not exceeding 1394 m2 (15,000 ft2). Draft curtains of non-combustible construction will be tightly
fitted to the underside of the roof or ceiling and extend down not less than one-eighth the distance
from the underside of the roof to the floor. Where permitted by roof structural framing systems,
curtains will be affixed to steel trusses, joists or similar framing. For applications involving sloped
roofs, draft curtains should run parallel with the roof slope.
3.9 Interior Finish. All interior finishes will have a Flame Spread Rating of less than 25 and a
Smoke Developed Rating of 50 or less.
3.10 Floor Drainage. Floor drainage systems will be provided to limit the spread of fuel to
mitigate the fire and explosion hazard from fuel spillage. Systems will be designed using
underground piping routed to a safe outside location.
3.10.1 The flow of liquids from helicopter hangar bay areas through wall openings will be
prevented by installation of drains, ramps, curbs, or other suitable means.
3.10.2 The slope of the floor in the helicopter hangar bay areas will be a minimum of one-half of
one percent. Floors will be sloped in the direction of trench drains located at the main hangar
doors or other location as required.
3.10.3 Determination of size of drainage piping will include consideration of the calculated
maximum demand of installed fire protection systems.
3.10.4 Oil Separators will be provided for drainage systems serving helicopter hangar bay areas.
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