15850 Laboratory and Industrial Ventilation Systems

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1 Part 1: General 1.01 General Guidelines - The primary purpose of chemical laboratory hoods and other industrial ventilation systems is to protect the worker or researcher against exposure to hazardous material in laboratories. The design should be considered on a case-by-case basis by the designer, after thorough investigation of the proposed usage and the materials to be used in the hood or system Selection / Procurement / Installation of Local Exhaust Devices - The installation of chemical hoods and other local exhaust ventilation equipment represents a facilities modification. These devices may be installed only by employees/contractors working for recognized campus design or maintenance organizations as part of an approved facilities modification process. Equipment selected must meet or exceed the specifications listed in this section Installation - No equipment covered under this section may be installed, modified, or removed by NC State employees or contractors, other than those reporting to Universitydesignated design, maintenance, or construction organizations. Part 2: Design Guidelines 2.01 General Requirements Design requirements for laboratory ventilation will follow ANSI/AIHA Z guidelines (or latest edition) unless pre-empted by information contained in this section or applicable sections of the NC Building Codes. Specific Applications shall follow the requirements listed in the latest version of the ACGIH Ventilation Manual unless covered in this section. Where specific design references do not exist, design parameters should be reviewed and approved by Facilities with input from Environmental Health and Safety as appropriate. The ANSI/AIHA Z9.5 guidelines do not apply to the lab ventilation for the following conditions: Laminar Flow Chemical Hoods: Contact NC State EH&S for requirements Biological Safety Cabinets: Meet NSF 49 requirements and requirements listed in NC State Biological Safety Manual Gas Storage Cabinets: Reference NC Fire Code, section 2203 Lab and industrial ventilation control systems: Contact George Smith Design must carefully consider acoustics and result in a laboratory noise level of NC (noise criteria) 50 or lower. Proper acoustic design should be accomplished by appropriate fan size and type. Sound attenuators are acceptable, though not preferred. When used, sound attenuators must be constructed of 304 stainless steel Lab ventilation rates must be maintained as follows: Rev 0 07/9/02 Page 1 of 10

2 Chemistry Lab 6-8 air changes per hour (ACH) based on the lab/building application and NC State EH&S hazard evaluation. In some instances, rates lower than 6 ACH may be appropriate for lower hazard (non chemistry) labs. In some instances, safety controls or temperature demands may dictate a design, which results in air change rates in excess of 8 ACH. In any case, where air change rates lower than 6 ACH or greater than 8 ACH are proposed, NC State EH&S and Facilities Division feedback and approval should be obtained at the earliest stage of design. Off-hour/night setback Typically 4 ACH and requires NC State EH&S and Facilities Division design approval Supply Air System The supply air system will be equipped with a reheat coil for humidity control Transfer air from non-hazardous areas such as offices shall be used whenever possible to provide make-up air for heavily exhausted laboratories. Supply air diffuser in laboratories shall be low velocity such that containment performance of chemical hoods is not affected Air velocity caused by supply diffusers, window drafts, lab aisle traffic, etc., shall be less than ½ and preferably 1/3 of the chemical hood average hood face velocity, measured 1.5 feet in front of the plane of the sash Supply air shall be properly balanced with hood exhaust in each room. Supply air shall be slightly less than exhaust air (except for clean rooms) to allow for laboratory rooms to be under negative pressure at all times, or hallways and stairways should be pressurized to produce negative pressure in a lab room. Pressurization shall be established by initial balance and maintained by linked supply and exhaust flow. Through the wall differential pressurization controllers are not allowed (except for clean rooms). Minimum differential pressure between laboratory and hallway/adjacent nonlaboratory spaces shall be maintained between 0.01 to 0.02 in. w.g. VAV systems shall be able to maintain the room differential pressure negative to hallway and adjacent areas, regardless of laboratory hoods sash position and/or other exhaust devices flow adjustment dampers position. For CAV systems, provision shall be made to ensure that room differential pressure is maintained unchanged (always negative to hallway and adjacent areas) when the hood sash (or other exhaust devices exhaust dampers) is closed. This may include techniques such as isolating the hood sash pocket from the area above the suspended ceiling. Supply air delivery must be designed to ensure hood performance and safety. Perforated ceiling/plenum supply air or perforated duct diffusers are acceptable. Rev 0 07/9/02 Page 2 of 10

3 Chemical hoods shall be located away from activities or facilities such as high traffic areas, air supply diffusers, doors, and operable windows, which produce air currents or turbulence. The minimum horizontal distance from a diffuser to the face of the hood should be 4' (four feet). The recommended minimum distance from lab entrance door to the hood is 10' (ten feet). Supply Flow Monitors - Workstations used for the control/exhaust of hazardous materials and which also contain HEPA filtered air supply system, shall include a differential pressure gauge to measure the static pressure drop across the filter. The static pressure reading must be readily visible at the operator s workstation. An audible readout from this monitor is optional. Maximum supply air velocity at the working stations (draft air speed) shall meet the ANSI/ASHRAE (or latest version) requirements Chemical Hoods Chemical Hoods Design Requirements Hood Type Only bypass hoods shall be selected for new projects. The bypass must be able to maintain the exhaust volume unchanged (<5%) when the sash is in the fully closed position. Bypass is not required for VAV hoods For VAV hoods and hoods with combination or horizontal sash, only a restrictedtype bypass system shall be used. The diversity factor for VAV systems needs to be evaluated by the engineer and on a case-by-case basis with feedback from NC State EH&S and Facilities Division. Auxiliary air hoods and ductless hoods are not allowed. Low velocity hoods do not provide significant additional energy savings (based on the NCSU design criteria of 100 ) and are not considered to be a viable approach. Should the designer wish to utilize this approach, provision of justification and receipt of approval from NC State EH&S and Facilities Division must be obtained at the earliest stage of design. A mechanical sash stop is required to limit the maximum vertical sash height at 18. Vertical sashes are preferred to horizontal sashes. Horizontal sash hoods (i.e. Sash with horizontal panels that cannot move vertically) are not allowed, unless written EH&S approval is obtained. Combination sash hoods are allowed if pre-approved by EH&S. Rev 0 07/9/02 Page 3 of 10

4 Combination sash VAV hoods need to have VAV sensors on both vertical and horizontal sashes. For a 5-foot hood, vertical sash opening shall not require more than 5 lbs force (for larger hoods, an additional one lb of force may be required for each additional linear foot of fume hood width) and sash should remain stationery when force is removed. ADA hoods shall be selected from an EH&S-approved list and will be installed in. above the finished floor for ADA compliance Hoods shall be equipped with a front edge air foils to reduce airflow eddies All utility valves and switches need to be located outside the hood. Non-electrical utilities may be installed inside the hood provided they have outside cutoffs and can be connected/operated without increased exposure risk or other unsafe conditions Fume hoods must be UL listed. The hood work surface should be recessed at least 1/8 in. with a seamless vertical lip to contain spills. If the hood is provided with a recessed sink, the perimeter of the sink shall also contain a 1/8 in. lip. Storage cabinets beneath the hood should be vented as long as it does not compromise hood performance (determined by local fire authority). The hood light shall be in a vapor resistant panel, accessible from outside the hood. The light shall provide a minimum of 80 foot-candle on any part of the bench level (36 form the floor). Chemical hoods (fume hoods) shall be designed to provide a continuous face velocity of 110 fpm at a sash height of 18. Final balance shall indicate 100 fpm at 18- inch sash height. Chemical hoods (fume hoods), which are designed to operate with variable air flow rates, shall draw a minimum rate of 25ft3 per sq foot of hood surface area, with the hood sash in the closed position. Deviation from this must be approved by EH&S. Exhaust Flow/velocity monitor and alarm All chemical hoods shall be equipped with an exhaust flow/velocity indicator and alarm to alert users to improper exhaust flow The flow/velocity alarm shall sound whenever average face velocity drops below 60 fpm. In addition to low flow alarm, a VAV chemical hood alarm shall sound when the sash is opened in excess of the design sash opening limit (18 ) Rev 0 07/9/02 Page 4 of 10

5 Hood Material Chemical hood material shall be non-porous and resistant to the chemicals Liner material shall be flame retardant, self-extinguishing and have a flame rating of 25 or less in accordance with ASTM-E84. The chemical hood sash needs to be constructed of shatter- proof transparent material, suitable for the intended use Chemical Hood Selection EH&S keeps an updated list of pre-qualified laboratory hoods for project managers to choose from. This list is developed based on the NCSU ASHRAE (or latest edition) test data, tests performed by other academic institutions, and data from hood balancing contractors. For a list of the pre-qualified hoods, refer to EH&S Laboratory and Industrial Ventilation Systems requirements: Selecting a chemical hood that is not included in pre-qualified list will require EH&S official approval 2.04 Exhaust System Exhaust system material shall be resistant to laboratory chemicals for the designed application A manifolded exhaust plenum on the roof is preferred in lieu of individual exhaust fans (i.e. 1 fan per hood or lab module). This does not apply to perchloric acid, acid digestion, and Iodination hoods. Hoods which are high hazard or unique use, such as perchloric acid, carcinogen glove boxes or radio iodination hoods shall not be installed in plenum-type systems and shall be separately exhausted. Manifolded exhaust systems are preferred, provided that they are designed in accordance with NFPA 30 and 45 (this requires that each laboratory unit have a dedicated exhaust system, which is manifolded with exhaust systems from other laboratory units unless such connection made above the roof level or otherwise exterior to the building). Manifolding of exhaust systems serving more than one laboratory unit must be approved by NCSU Facilities and NCSU Environmental Health and Safety prior to design. Provisions should be made for local exhaust of instruments, gas cabinets, vented storage cabinets or special operations not requiring the use of a chemical hood (local capture devices). Exhaust discharges from vacuum pumps shall be hard piped to local exhaust systems. Inserting the exhaust tube into the exhaust drop without a sealed connection is not acceptable. Rev 0 07/9/02 Page 5 of 10

6 Exhaust systems for systems such as gas cabinets or processes shall be monitored with a monitor similar to that used for chemical hoods with the exception that it shall have an auxiliary relay for connection to a process control system. NCSU has a standard design for this control panel. Gas cabinets for gas cylinders shall be in accordance with the building codes and shall be designed with an average face velocity of 200 FPM at the inspection door, when the inspection door is opened. To optimize and/or adjust exhaust flow to levels required for hazard control, flow adjust devices such as dampers shall be installed in each exhaust duct branch connected to exhaust devices. Exhaust Fans Exhaust stacks shall be high velocity type, with a minimum of 3000 FPM with preferable velocities approaching 4000 FPM. In congested areas, an analysis of the air patterns at the roof level may be required to insure that contaminated exhaust air is not re-entrained into building make-up air and that the exhaust air is discharged beyond the boundary layer of the building For manifolded exhaust systems the fan set shall be of the Strobic or MK Plastics high plume, induced air type. Preferably, fans should be direct drive. Air induction shall take place downstream of the fan impeller. Fans to have stainless, motorized isolation damper. Depending on system size, one fan shall provide stand-by with the capacity to match one of the remaining fans For an individual hood exhaust set: Exhaust stacks shall extend a minimum of 10 ft. above adjacent roof lines andair intakes in a vertical up direction Guy wires shall not be used to support exhaust stacks unless the stack is of unusual height. In general, exhaust stacks may be supported by bolting to a flanged fan discharge or by extending support steel from the fan support curb or steel frame. In general, exhaust stacks shall have a coned discharge to achieve discharge velocity. On a regular basis, fans shall be provided with a zero-loss style exhaust discharge. All fans shall be provided with a drain and ball valve in the bottom of the scroll. For manifolded systems, there shall be at least two exhaust fans for redundancy, and at least one fan shall be connected to emergency power. Emergency power, pressurization, and emergency exit (Ken) Exhaust duct Rev 0 07/9/02 Page 6 of 10

7 General-purpose chemical hood ductwork shall be butt-welded 304 stainless steel with 304 stainless steel fillet material. Flanged joints may be used only where field conditions prevent welded joints. Iodination hoods ductwork shall be butt-welded stainless steel. Perchloric ductwork shall be fire resistant fiberglass. Iodination and biological hoods shall be adequately filtered prior to connection to a centralized exhaust system Downdraft Exhaust Systems Downdraft tables are recommended for anatomy lab dissection tables and may be appropriate for certain lab benchtop applications. Proposed designs should be discussed with Facilities and EH&S at the earliest opportunity in the project Perchloric Acid Hood and Exhaust Systems Laboratories that utilize perchloric acid require a specially designed fume hood dedicated to perchloric acid use. A perchloric acid hood is a specialized stainless steel hood with non-reactive/acid resistant duct and exhaust fan, and built-in water wash-down system, designed to prevent the deposition and a build up of explosive perchloric salts on the hood and exhaust system. For specific perchloric acid applications, laboratory design may exclude perchloric acid hood installations. However, this can be carried out only after EH&S written approval. Perchloric acid hoods and exhaust systems shall meet the ANSI Z9.5 and NFPA 45 requirements Connecting Perchloric acid hood ductwork to other exhaust equipment is prohibited. Hoods, exhaust ductwork, fans, gaskets, and other material/components shall be constructed of acid resistant, non-reactive, impervious materials. All duct work seams and joints shall be welded. Hood baffles shall be removable to allow for periodic inspection. Ductwork shall take the shortest and straightest path to the outside. Positive drainage shall be provided back to the hood. A water spray system shall be provided to wash down the entire exhaust system from the hood interior behind the baffle, through the fan, up to the roofline. The hood work surface shall be watertight with a minimum depression of 1/2 inch at the front and sides. An integral trough shall be provided at the rear of the hood to collect wash down water and direct it to a drain. The baffle shall be removable for cleaning. Provide a hose bib within 40 feet of the discharge stack to allow for manual wash down. Provide controls so that the user can easily initiate wash down. Provide an automatic wash down cycle. The duration of the automatic cycle depends on the configuration of the ductwork. Because wash down of a contaminated hood requires up to 24 hours of continuous washing, provide for manual override of the automatic cycle. Rev 0 07/9/02 Page 7 of 10

8 Provide an easily readable placard stating: "Wash down often. Perchloric acid (HClO4) can violently decompose on contact with organic compounds such as acetic acid, alcohols, ketones, aldehydes, ethers, dialkyl sulfoxides, paper, wood, grease or oils. Perchlorate compounds formed by reaction with heavy metals, alkali metals, ammonium or some organics are shock sensitive explosives." 2.07 Acid Hoods (non-perchloric) Acid hoods must be considered for acid digestions, large volumes/high temperature ((e.g. boiling)) acid applications,. Acid hoods might be built with or without a water wash down system. Review with EH&S for wash down system requirements Connecting ductwork from water wash hoods to other exhaust equipment is prohibited. Hoods, exhaust ductwork, fans, gaskets, and other material/components (e.g. light fixtures) shall be constructed of acid resistant, non-reactive, compatible, and impervious materials. Ductwork shall take the shortest and straightest path to the outside. Positive drainage shall be provided back to the hood Testing/Commissioning Airflows in hoods must be certified. The air flow quantity of each hood must be tested by an independent testing agency. The results must be certified by the contractor and engineer and submitted to Facilities Planning and Design. Balancing/Approval for Use - Balancing is required for chemical hoods, gas cabinets, laminar flow chemical hoods, and other exhausted devices where hazardous materials are stored or used. Vacuum pump exhausts do not require balancing. Where balancing is required, it will be performed by persons certified by the Associated Air Balance Council (AABC) or the National Environmental Balancing Bureau (NEBB), unless otherwise indicated by Facilities Planning and Design. Where certified balance contractors are not required (e.g. single-hood installations), hood adjustment and initial balancing will be performed according to manufacturer s instructions (unless otherwise indicated in this document) and flow measurements conducted in accordance with NC State flow testing procedures. A white sticker containing hood identification information shall be applied by the balancing contractor to the face panel of the exhaust device. Where this is not practical, the sticker can be applied to the duct that is measured. Duct traverse pilot holes shall be capped with a removable plug to allow for future readings at the same location. Stickers applied to ductwork should be located near the monitoring point for clarification. Laboratory chemical hoods and laminar flow chemical hoods may not be used until Environmental Health and Safety receives the completed NCSU New and Renovated Fume Hood Construction From (Form FH-1) from the CPM, verifies proper flow/installation/calibration, and applies a green label to the face panel.. The final test shall be requested after the installation is complete, the building ventilation Rev 0 07/9/02 Page 8 of 10

9 system is balanced, all connections are made and all control devices are calibrated/adjusted, and CPM has completed and submitted the FH-1 form to EH&S. All newly installed laboratory chemical hoods (100%) shall be tested to As Installed (AI) EH&S test criteria, developed based on the ASHRAE (or most current edition) and ANSI Z9.5 (latest edition), as specified in EH&S Laboratory and Industrial Ventilation Systems requirements: ( A qualified third party (approved by EH&S) shall perform the AI tests on 100% of the installed chemical hoods., If AI test reveals any hood design/installation deficiency, the manufacturer/contractor shall remediate the deficiency and repeat the full ASHRAE 110 test (EH&S test criteria). The manufacturer/contractor would be financially responsible for all additional tests required after modifications/repairs are made. A chemical hood that does not meet the ASHRAE 110 test criteria even after modifications shall be replaced. Test data shall be electronically imported from instruments The AI containment test shall include: Exhaust Flow Measurement Hood Static Pressure Measurement Face Velocity test (adjusted to fpm) Cross draft velocities Airflow visualization (small and large volume smoke test) Tracer Gas Containment Test (static and dynamic) Hood monitor calibration check Room pressurization check VAV hoods require additional commissioning tests: Flow/face velocity measurements at different sash heights (full open, 18 and 12 ) o VAV systems shall prevent flow variations in excess of 10% from design at each sash location. VAV response time measurement o A response time of <3-5 sec. after the completion of the sash movement is acceptable o. Fume hoods will be released for users after tests are final, system is fully commissioned, and EH&S test/evaluations indicates no defects/malfunctions Other local exhaust ventilation systems Canopy hoods Rev 0 07/9/02 Page 9 of 10

10 Canopy hoods provide limited protection and shall not be used to control exposure against hazardous materials in laboratories. Canopy hoods may only be used for non-hazardous odor or heat control at the source. Canopy hood design shall meet the ACGIH Industrial Ventilation guidelines and requires EH&S pre-approval Slot hoods, snorkels, and special design/purpose hoods These local exhaust devices provide limited protection compared to a fume hood and shall not be used as the primary engineering protection or as a replacement for chemical laboratory hoods unless the application is approved by NC State EH&S. In some cases, this method can provide acceptable contaminant controls with reduced energy consumption. Design shall meet the latest ACGIH Industrial Ventilation guidelines. Design and installation requires EH&S approval Ductless hoods Because of limited protection, ductless hoods are not permitted for use at NCSU. Contact EH&S for additional information. Exhausted laminar flow chemical hoods with built-in supply blower Contact NC State EH&S for selection and balancing information Selecting exhausted Biological Safety Cabinets (class II type B2 or higher) that are directly connected to the building exhaust system must be approved by EH&S Glove box: - Glove boxes shall meet the requirements of ANSI Z (or latest edition) Balance Enclosures Exhausted balance enclosures shall meet all fume hood requirements listed/referenced in this document. Using balance enclosures that return air back into the laboratory after filtration requires EH&S hazard evaluation and preapproval. Rev 0 07/9/02 Page 10 of 10