Design Standard - Fume Hoods & Fume Hood Exhausts

Transcription

1 1.0 Intrductin Design Standard - Fume Hds & Fume Hd Exhausts The fume hd is the primary cntrl device in mst labratries fr prtecting emplyees and students frm expsure t hazardus chemicals. It is als an integral part f the building air handling system. The efficiency f peratin is essential in maintaining gd air quality in labratries. It is therefre imperative that it functin prperly and that it be designed apprpriately. This standard was develped in accrdance with the Canadian Standards Assciatin (CSA) Standard Z Fume Hds and Assciated Exhaust Systems. 2.0 Applicatin This standard primarily applies t prject managers verseeing the design and installatin f a fume hd system n campus and t faculty r staff at the University f Trnt that may be invested in such a prject t the pint where their expertise r guidance may be required fr the design prcess. This includes installing new fume hd systems r the replacing an existing fume hd system r cmpnent f a fume hd system. The purpse f this standard is t ensure that any cmpnents f a new r replacement system cmply with the mst recent CSA standard and any relevant legislatin. 3.0 Definitins ASHRAE: American Sciety f Heating, Refrigerating and Air Cnditining Engineers. Bypass Fume Hd: A fume hd that cntains an pen grill/luver abve the frnt face f the wrking chamber. This grill cmpensates fr the reductin in face area, and thus the significance f face velcity changes, when the sash is perated. Wrking Chamber: The sectin f the fume hd system that includes: The fume hd sash; The fume hd wrk space; The structural frame f the fume hd. 4.0 Respnsibilities 4.1 Prject Managers Prject managers that are managing a fume hd system installatin r mdificatin prject are respnsible fr:

2 Adhering t the design requirements f this standard; Infrming the Office f Envirnmental Health and Safety f the prject; Prviding all infrmatin that the Office f Envirnmental Health and Safety requests regarding the prject; Mdifying the design, as necessary, t ensure the cnditins f this standard and cmpliance requirements are met; and Ensuring the prject is implemented as designed. 4.2 The Office f Envirnmental Health and Safety (EHS) The Office f Envirnmental Health and Safety is respnsible fr: Where pssible, prviding guidance when requested and required t help ensure that the fume hd system s design meets this standard and cmpliance requirements; and Maintaining this standard. 5.0 Design Standard The fume hd is ne cmpnent f the expsure cntrl system; its perfrmance therefre cannt be judged in islatin frm the rest f the system. The ttal system cnsists f: The wrking chamber; The exhaust system; Fume hd lcatin; Make-up air t the fume hd; System indicatrs; Operatinal parameters; and System maintenance. The fllwing specificatins prvide the standard fr acceptable perfrmance and efficiency f fume hd systems; all new installatins shall cnfrm t these specificatins and existing installatins shuld be brught t this standard as funding permits. 5.1 The Wrking Chamber

3 The wrking chamber shuld: Be by-pass type when cnstant vlume systems are required; Be cnstructed frm nn-flammable, acid/crrsin resistant materials; Include a back baffle system t mre evenly distribute the air acrss the face f the chamber such that unifrm air flw thrugh the face f the fume hd will result; Include a stainless steel air fil alng the lwer, frnt edge at the face f the fume hd wrkbench which prvides a streamlined and aerdynamic entrance prfile; Include vertical and/r hrizntal sliding sash t minimize the size f the wrking aperture and t act as a safety screen. The sash shuld be cnstructed f transparent glazing that is resistant t disclratin and crazing by age r expsure t chemicals; and Cntain a recessed wrk surface t retain spilled liquids. The wrk surface must be able t bear the weight f any equipment r radilgical shielding material that is required. Be labelled with a unique identifier. This identifier shuld als be labelled n: The fume hd fan; and The exhaust stack. 5.2 The Exhaust System Fume Hd Ducting The fume hd ducting shall: Be designed t prvide ptimum air flws in the wrking chamber; Be designed and sized t minimize nise levels frm fume hd fan peratin; Avid hrizntal runs as much as feasible t minimize cllectin f crrsive cndensates; Where hrizntal runs d exist, the duct must slpe at least 2.5 cm dwnward t a suitable drain, in the directin f airflw, per 3 meters f hrizntal run;

4 Cntain circular crss-sectin t reduce the number f crners and crevices where crrsin might ccur; Be cnstructed with type 316 stainless steel welded cnstructin, except where the chemicals used require cmpatible materials; Ensure that these materials cmply with the requirements f the Ontari Building Cde and the Fire Cde Fume Hd Exhaust Fan The fume hd exhaust fan shall: Be fitted with flexible cuplings which cnnect the fan t the ductwrk that are made f a fabric which is highly resistant t a wide range f chemicals and envirnmental cnditins; Be lcated s as t ensure that the exhaust ducting belw the fan within the building remains at negative pressure and the ducting abve the fan remains at psitive pressure; Be lcated in a well-ventilated lcatin; and Be f sufficient capacity t maintain negative pressure and peratinal parameters (See sectin 5.6 fr peratinal parameters) f all cnnected fume hd cabinets Radiatin Fume Hd Exhaust The fume hd exhaust stack shall: Discharge vertically upwards at a velcity f at least 1.4 times the average wind velcity; Be s psitined as t ensure that emissins are unable t re-enter the building r adjacent buildings; The recmmended minimum straight-line distance between the exit pint f the exhaust and the building r intake pening is 15.24m; Fr new buildings, be at least 3.05m abve the highest pint f any adjacent buildings; Where pssible t determine the prevailing wind directin, be dwnwind f any air intakes; and

5 Be attached t a prperly installed trap and drainage system Envirnmental Cmpliance Apprvals Ntwithstanding any f the abve, the fume hd must meet all Envirnmental Cmpliance Apprval (ECA) requirements. The Office f Envirnmental Health and Safety requires that all needed mdelling f prpsed exhaust stack lcatins and is cnducted and can recmmend any required mitigatin f r alteratins t a fume hd installatin prject. 5.3 Fume Hd Lcatin A fume hd shall be lcated: In such a way as t minimize risks t persns in the event f fire r explsin; Away frm predminant ft-traffic areas (drway, etc.); and Away frm majr air patterns r equipment that prduces crss-draughts. 5.4 Make-Up Air t the Fume Hd Make-Up Air shall: Be prvided t replace air exhausted by the fume hd; Be at a suitable temperature t avid wind chill effects; and Nt significantly disturb the airflw pattern in the fume hd; Diffusers shall nt push air directly int the face f the fume hd; Air that is pushed frm diffusers parallel t the face f the fume hd shall nt have a velcity that exceeds 50% f the as used face velcity f the fume hd. 5.5 System Indicatrs and Alarms All University f Trnt fume hds must be fitted with an alarm device: On the frnt f the fume hd; That indicates t fume hd users that the fume hd is nt functining prperly. All UfT fume hd alarms must: Have an audi indicatr f fume hd failure;

6 Have a visual indicatr f fume hd failure; and Be accessible at all times. All UfT fume hd alarms shuld: Have user accessible cntrls that d nt require third party (nn-uft) access fr repairs r recalibratin; All UfT fume hd alarms may: Have a digital display f current fume hd cnditins; Have a pwer switch; Have flw cntrl; and Have an audi level cntrl Fume Hd Alarm Design Restrictins The fllwing design restrictins apply t UfT fume hd alarms: Fume hd alarms that rely n pressure switches shall nt be used n variable air vlume fume hd systems. 5.6 Operatinal Parameters Standard Variable Air Vlume and Cnstant Air Vlume Fume Hds When the fume hd is in peratin, the air velcity thrugh the face f the fume hd at a minimum f ne perating sash height, which is n lwer than 12 inches abve the airfil and n higher than 18 inches abve airfil must be: N less than 80 feet per minute; N greater than 130 feet per minute; and Relatively unifrm acrss the entire aperture High Efficiency Fume Hds Fr high efficiency fume hds, the peratinal parameters will be determined using an ASHRAE cntainment test. Therefre, peratinal requirements fr high efficiency fume hds may vary and will be determined n a fume hd by fume hd basis and will be based n the utcme f ASHRAE testing.

7 The University f Trnt Office f Envirnmental Health and Safety can prvide the ASHRAE testing at a prject cst f $200 per hd. Third party rganizatins can be cntracted t cnduct the testing in place f the EHS ffice, hwever the EHS ffice shuld be cnsulted, at n charge, t help address any cntainment issues that may be revealed by the ASHRAE testing prcedure High Efficiency Fume Hd Imprtant Cnsideratins There are sme additinal planning cnsideratins that are recmmended fr high efficiency hds. These recmmendatins may prevent additinal csts and/r unfreseen cmplicatins prir t cmmissining: Where pssible, avid installing a high efficiency fume hd system in a preexisting labratry withut als retrfitting the make-up air system t be better suited t the fume hd s reduced air flw and cntainment needs; Install sashes with autmatic clsers that activate a few minutes after the hd becmes unccupied in rder t prevent walk-by wake effects that cmprmise cntainment in pen, but unccupied hds; and When designing the exhaust system, allw fr extra fan capacity in case the flw in the fume hd must be increased in rder t achieve cntainment Fume Hds fr Radiactive Materials Fr fume hds used fr nuclear substances: The wrking chamber will be marked with a radiatin warning sign; Any accessible sectins f fume hd exhaust ducts cnnected t a radiatin fume hd must be marked with radiatin warning symbls at intervals n greater than every 3 metres; If the fume hd is used fr radiactive material strage, then the fan servicing that fume hd must remain peratinal at all times; If the fume hd is used fr radiactive material strage, then it must remain under negative pressure, belw the fan, at all times; If the fume hd is used fr cntinuus exhausting f radiactive substances, then: The exhaust fans will be cnnected t an emergency pwer system; and

8 The fume hd exhaust will nt cnnect with ther exhaust systems. The fume hd will nt cntain any kind f air filtratin. If filtratin is required, then: Radiatin mnitring and change ut schedules must be cnfirmed with the Radiatin Safety Officer. 5.7 Ductless Fume Hds Ductless fume hds are nly t be used if apprved by the Office f Envirnmental Health and Safety, and nly in situatins where a fume hd is abslutely required and a ducted fume hd is nt a feasible ptin. Lab supervisrs r managers that wish t use a ductless fume hd in place f a ducted fume hd must be able t make the fllwing infrmatin available t the EHS Office at all times: A filter change-ut schedule; Current recrd f filter changes; and An assessment f filter cmpatibility with respect t the chemicals that are planned n being used in the fume hd 6.0 Dispersin Mdeling Prir t a new fume hd system r exhaust stack installatin apprpriate dispersin mdeling will be cnducted by: 1. The University f Trnt EHS Office 2. A party that has been delegated respnsibility by the UfT EHS Office t cmplete the dispersin mdeling. A new fume hd system r exhaust stack cannt be installed until: 1. Dispersin mdeling f the prpsed system has been cmpleted; and 2. The dispersin mdeling results adequately demnstrate that the new fume hd system r exhaust stack will nt put the UfT ut f cmpliance with: a. Existing Envirnmental Cmpliance Apprvals granted t the UfT by the Ontari Ministry f the Envirnment; and b. The Ontari Envirnmental Prtectin Act, Sectin 9.

9 If the dispersin mdeling results indicate that the prpsed fume hd system r exhaust stack will put the UfT ut f cmpliance with envirnmental regulatins, then the lcatin r specificatins f the prpsed fume hd system r exhaust stack must be mdified until the dispersin mdeling indicates cmpliance. 7.0 Fume Hd Cmmissining All fume hds at the University f Trnt must be cmmissined befre they can be used. Cmmissining is cnducted by the University f Trnt Office f Envirnmental Health and Safety. The cmmissining prcess requires: Evaluatin f the installed fume hd system with respect t this design standard; Measurement f fume hd peratin parameters; Testing f the fume hd alarm system; ASHRAE testing f: The 20% f all hds installed as part f a single prject r all hds installed as part f a single prject if less than 20 hds were installed. All high efficiency hds. Cmmunicating any discrepancies fr crrectin t the prject and lab manager; and Cnducting the cmmissining prcess again fllwing any such crrectins. 8.0 Standard Revisins On an annual basis, the University f Trnt Office f Envirnmental Health and Safety may evaluate this standard with respect t: Efficacy; Changes in the guiding standards r legislatin; Applicability t UfT peratins; Relevance and functinality f the standard with respect t the regulatry requirements and safety; Clarity f the standard and prcedures t all respnsible parties; and

10 Feasibility f implementatin and management f the standard. If, upn evaluatin, gaps are identified with respect t the evaluatin criteria, the standard may be revised in such a way as t crrect thse gaps.