hI'J]48'i'12.8'Air Serv. Eev. Eev. Floor Area • Watersupp y!5 2"0 Shaft ShaftSupplyVestibule·suShaftI Air mJ"sm~~(~ .,;,-Exh. /Sh~ L~_jShaft:l*.!:.11-.1~ ~.-Crib, 4' X 4' X 3'Viewing1-->r,-: \ LArea00West COII:idor 1 5'"'Notes:* = pendent sprinklerFigure 2including data-processing areas, are listed. as "light hazard"in NFPA Standard 13. That is, "quantities and/or combustibility<str<strong>on</strong>g>of</str<strong>on</strong>g> c<strong>on</strong>tents are low and fires with relatively low rates<str<strong>on</strong>g>of</str<strong>on</strong>g> heat release are expected" (NFPA 1991). No values arestated in .NFPA Standard 13 to quantify what c<strong>on</strong>stitutes a"relatively low" heat release rate (HRR), ·which is notsurprising, given that it depends <strong>on</strong> the specific occupancyarld compartment c<strong>on</strong>diti<strong>on</strong>s. Various authors have treatedwood cribs as representative <str<strong>on</strong>g>of</str<strong>on</strong>g> light hazard fuel packages(Walt<strong>on</strong> 1988; Madrzykowski and .Vettori 1992). A woodcrib canilot completely simulate "real" burning c<strong>on</strong>diti<strong>on</strong>s,however, in that the fuel is c<strong>on</strong>centrated in a limited· arearather than· distributed over a large space. All <str<strong>on</strong>g>of</str<strong>on</strong>g> the fuelwithin the crib can bum at <strong>on</strong>ce, whereas fuel distributedQver a larger area will bum sequentially as fire spreadsfrom <strong>on</strong>e object to another .. For test purposes, it waspractical to use wood cribs that produced an HRR representative<str<strong>on</strong>g>of</str<strong>on</strong>g> a typical <str<strong>on</strong>g>of</str<strong>on</strong>g>fice workstati<strong>on</strong> in which a certain mass<str<strong>on</strong>g>of</str<strong>on</strong>g> fuel is c<strong>on</strong>centrated within a relatively small area.Madrzykowski and Vettori (1992) tested typical <str<strong>on</strong>g>of</str<strong>on</strong>g>ficeworkstati<strong>on</strong> fuel packages c<strong>on</strong>sisting <str<strong>on</strong>g>of</str<strong>on</strong>g> a desk, table,padded chairs, boxes <str<strong>on</strong>g>of</str<strong>on</strong>g> paper partially shielded under thedesk, etc., weighing a total <str<strong>on</strong>g>of</str<strong>on</strong>g> 639 Jb (290.5 kg). Averageheat release rates during unsuppressed burning <str<strong>on</strong>g>of</str<strong>on</strong>g> this fuelpackage were reported to be approximately 570 Btu/s (600kW), with several peaks as high as 1,235 Btu/s (1,300 kW)as various comp<strong>on</strong>ents <str<strong>on</strong>g>of</str<strong>on</strong>g> the package ignited sequentially.Madrzykowski and Vettori's workstati<strong>on</strong> HRR results canbe used as a benchmark for comparis<strong>on</strong> with the wood cribfires used in these tests.Wood cribs <str<strong>on</strong>g>of</str<strong>on</strong>g> two sizes were used in these experiments.·In the 10-story tower, cribs weighed approximately600 Jb (272 kg). The unsprinklered heat release rate fromPlan <str<strong>on</strong>g>of</str<strong>on</strong>g> the J().story tower, seventh floor.these cribs was measured at 1,150 Btu/s (1,200 kW). Theywere 66 lb (30 kg) heavier than the workstati<strong>on</strong>s describedin Madrzykowski and Vettori (1992); however, the exteriorrows <str<strong>on</strong>g>of</str<strong>on</strong>g> wood in the cribs, which were wetted by sprinklerspray, did not bum. The actual weight <str<strong>on</strong>g>of</str<strong>on</strong>g> fuel c<strong>on</strong>sumed byfire was typically 350 Jb (160 kg), or about 50% <str<strong>on</strong>g>of</str<strong>on</strong>g> theinitial crib weight (Mawhinney et al. 1992). These woodcribs compare reas<strong>on</strong>ably well to the light hazard fuelloadings representative <str<strong>on</strong>g>of</str<strong>on</strong>g> an <str<strong>on</strong>g>of</str<strong>on</strong>g>fice occupancy described inMadrzykowski and Vettori (1992).In the tests in the <strong>on</strong>e-story room, larger wood cribswere used, typically weighing 1,200 Jb (545 kg). Again, notall <str<strong>on</strong>g>of</str<strong>on</strong>g> the fuel could bum because <str<strong>on</strong>g>of</str<strong>on</strong>g> wetting <str<strong>on</strong>g>of</str<strong>on</strong>g> the wood <strong>on</strong>the outer edges <str<strong>on</strong>g>of</str<strong>on</strong>g> the crib. Unsuppressed, and with themaximum ventilati<strong>on</strong> that could be provided in the <strong>on</strong>e-storyroom, a peak heat release rate <str<strong>on</strong>g>of</str<strong>on</strong>g> 2,850 Btu/s (3,000 kW)was measured for these cribs. Most <str<strong>on</strong>g>of</str<strong>on</strong>g> the tests werec<strong>on</strong>ducted at Jess than full ventilati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>s, however,which limited the heat release rate <str<strong>on</strong>g>of</str<strong>on</strong>g> an unsuppressed fireto 1,900 Btu/s (2,000 kW). These cribs did not represent alight hazard fuel loading, but, as stated earlier; the P.rimaryobjective <str<strong>on</strong>g>of</str<strong>on</strong>g> the testS in the <strong>on</strong>e-story room was to evaluatethe nature <str<strong>on</strong>g>of</str<strong>on</strong>g> the interacti<strong>on</strong> between sprinklers and the fire.This co.uld be dqne by creating a fire that could be sus·tained at relatively steady-state c<strong>on</strong>diti<strong>on</strong>s for a l<strong>on</strong>g time,while ventilati<strong>on</strong> and sprinkler density were varied.Wood. cribs were c<strong>on</strong>structed using 3.5-in. by 3.5-in.(90-mm by 90-mm) dry white pine sticks, spaced 3.5 in.(90 mm) apart and piled 10 rows (36 in. [0.91 m]) high. Inthe <strong>on</strong>e-story room, sticks were 70 in. (1.78 m) .l<strong>on</strong>g; in thetower, 48 in. (1.22 m) l<strong>on</strong>g. The total mass <str<strong>on</strong>g>of</str<strong>on</strong>g> wood in thecribs in the <strong>on</strong>e-story room was typically 1,200 lb (545 kg);those in the Tower were <strong>on</strong>·~verage 700 Ib (320 kg).ASH RAE Transacti<strong>on</strong>s: Research497
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