2000 HEWITT AVE EVERETT EVENT CENTER 2016-01-01 MF Import

08%12i2009 09:20 FAT 1 J25 JJ9 8287 HERMANSON �007�00� 1997 UMC HANDBOOK JY 507.6 Duct Enclosure. F�gurc 5-8 illustrates a number of Mechanic�l Code requuemenu applicable to a commercial kitchen cxhaust system.A greau duct strving a Type I hood that peneuates a ceiling, wall or floor must be enclosed in a duct cnclosue from pomt of peoetration to tl�e outside air. A dud may only penetrate extecior walls az locatioa,where�mtected openings azc pernvtted by t1�c Building Code.A greast duct cnclosure is coastruded like a shatt enclosure as covered by the Building Code;however,all iequirements aze included in the tJMC. UBC Section 71 l requirements are not applicable to grease duct enclosures. Duct enclosurEs must be of at]east one-hour fire-resistive coasliuction in all build'mgs ar:d of two-hour fi�-rcsistive conshuctiun in Types I and II Sre-raistivc buildings. The duct cntlosiue must be sealcd at the point of penetiaUon of ffie ceiling,wall or floor and vented to the extcnor through weather-proteeted oponings. The duct cnclosure must be separated from the dua b}•at least 3 inchcs(76 mm)and not more than 12 inches(305 mm),�d it must serve onl�a single�'casc exhaust duct system.The Untjorm Mechaniaal Code does not require tk�at a makeup air duct rcquircd by Sedion 402.4 be enclosed in a duM enclosute.However, some designs of factory-built compensadng hoods have the makeup ait duct IocaDed so close to tFtc grease exhaust duct that it is impossible to separau the ducts with a duct enclosure; in fact,ar least one listed compensating hood has the makeup air dud entirelv sur roundin�the grease exLaust ducx. In those instances, both ducts should be fabricated of 16 gage steel and installed 'u�the same enclosuro. When a Tvpe I l�ood penetrates a ceiling,wall or furced space, Scction 508.4 requires ihai thst portion be endosed in an enclosure as required by Sedion 507.6. If a compeasating hood makeup air duct penetrates the grea,ae duct enclosure,it should bc either rncloscd in a rafed enclosure or it should be equipped cvith a fire damptr. One frequently asked question is whether the special pmvisioac of UBC Section 711 mean that a gcase duct eaclosure is not required in rno-and tbree-stocy buildiogs. Unr'fonn Buildirtg Cade Section 7l I deaLs with shaft enclosures protecting openings in tloors. A grcasc duct cnclosurc rcquircd by Scetion 507.6 may run horizonis:ly as wcll as��ccticapy,but its principal pucposc is to ptcveu[thc duce,which may bc n:d hot when grcace is buming in its interior;from acting as a source of ignition for combustible materials exposed to its cadiant eaerg}�. By enclosing every portion of a concealed grease duct w�thin at least one-hour Sre- resistive coasmicrioq even in a one-story building,the radiation is contame�and unril the duct enclosure fails, other parts of the suvchue w�ill be unaffecte� 7'he intent of tl�e reference to the Building Code here is to ensure tLat a grease duct is enclosed by a construcdon having a full one-hour or Avo-hour fire-nsistivc roting az indieated in UBC Tnble 7-B. The reY'zrence to the Building Code should not be construed to permit the inscallation of conccaled greasc ducts wzthout being enclosed in a iated greaSe duct cntlosurc. The intent ofthe requiremcnt that the duct enclosurc be separaied from the grease duct by at least 3 inches(76 mm)and not more tfian 12 inchts(305 mm)is to crcate an air space surrounding the dua tl�at is sealed at iu lower end aud vemed to the exterior above the roof.The purpose ofthst air space or annulus is ro provide waming to fire service personael on the toof of the building whcn the greue dud has been penetiated by fire.ln the scenario esplaining the sequence of the fire development, it was thcorized thaz during the earliest srages of a gease du�t fire, flames �vould bc confiucd within the dua itself and appear onty at the exhaust urmination above the roo£ As the fue progresses;the grease duct will be burned tluough and Flames w'ill then appear both at the e�haust temtinaiion and at d�e veM az the top of ihe grease duct enclonue. Because of the liniited firc resi5tan�e of a gtr.�se duct enCloSure,the fire scrvicc personncl «routd be wamed tha[sVuctural integriry of the roof�tiss bcin�thrcatcncd and thac it would bc prudcrrt to cvacuatc thc roof top. The n:quircd ma.Umum separation of 12 inches(305 mm) was imposed to discourage othcr usc� of the annulaz space, such•rs for electrical aving and piping,and to facilitsie elraning the duct tivough openings in thc dua enclosure. �,�3