Element D Services Heating Ventilating and Air Conditioning ODG010107 D304202 Laboratory Exhaust and Ventilation Part 1. General 1. This section supplements Design Guideline Element D3042 on air handling distribution with specific criteria for projects involving design of Laboratory Exhaust and Ventilation Systems. 2. Refer to Design Guideline Element D3042 for the following: a. General design criteria related Exhaust and Ventilation. b. Special Contract Document Requirements and products applicable to the Project. Part 2. Design Criteria GENERAL 1. In general, laboratory exhaust systems shall comply with procedure and support room ventilation air requirements of NFPA 90A, NIH, CDC, and OSHA. 2. Special exhaust systems, noted below, are hazardous and shall not be housed in the same chase that houses environmental supply, return, and exhaust ducts. a. Laboratory hood exhaust systems. b. Biological laboratory exhaust. c. Radioactive hot lab exhaust. 3. All other ductwork carrying make-up air that is connected to special exhaust systems may be installed in the same chase that carries environmental supply and/or return ducts. 4. Fans shall be connected to an emergency power source. LABORATORY HOOD EXHAUST SYSTEMS 1. Fume hoods and biological safety cabinets require dedicated exhaust systems. While the type of exhaust system would depend on the hood characteristics, the following features shall be incorporated into the design to avoid excessive noise levels and ensure accurate air balancing. a. The system shall conform to OSHA Regulation 29 CFR, Part 1910. b. Exhaust shall be continuously monitored and an alarm system (local audible and visible alarm and an alarm at M. D. Anderson Cancer Page 1 of 5
Center s central monitoring services, shall be provided for each hood and biological safety cabinet). c. Exhaust fans shall be selected to operate at low tip speed (approximately at 50 percent of the maximum permissible tip speed) and maximum static efficiency. d. Provide fan selection data on a performance curve and ensure that the fan discharge is directed vertically upward with a discharge velocity greater than 3000 fpm. e. Minimum stack height shall be 12-feet. f. Design duct sizing to maintain velocity in the ductwork between 2000 and 2500 fpm. g. Select fans with backward inclined fans. h. Perform sound analysis for each exhaust fan and provide sound attenuation, if required. i. To ensure design airflow is achieved, pressure independent, factory-set, field-adjustable automatic airflow control shall be provided for each fume hood and biological safety cabinet. 5. Each laboratory exhaust air system shall have a corresponding supply air system to comply with laboratory, hood exhaust air, and laboratory ventilation exhaust air change requirements listed below: Room Description Occupied AC/ hr Unoccupied AC / hr Fume Hood 10 6 Rooms Radio Chemistry 10 6 Laboratory 12 6 Tissue and Culture 12 8 Dark Room 10 10 Storage Room 4 4 Glass Wash Room 10 6 6. Air change rates noted above are minimum air change rates during occupied periods. Actual air change rates may exceed the stated rates due to sensible heat gain or make-up air requirements. 7. Laboratory exhaust fans and 30 percent filter banks shall be an N+1 redundant system capable of maintaining constant volume with the capacity to exhaust listed rooms at the required minimum ventilation design air change rates. 8. Exhaust fans shall be direct drive and powered though the use of variable frequency drives that vary fan speeds to maintain the exhaust air requirement during exhaust air filter loading. Fan speed is determined by maintaining and airflow measurement setpoint (adjustable) from the building automation system (BAS). 9. The design exhaust rate through the fume hoods, radioisotope fume hoods and (BSCs) will be determined based on using restricted sash opening and maintaining a minimum face velocity of 100 fpm at any point at the open sash. Page 2 of 5
Laboratory chemical hood Operation - Face Velocities should be between 80 and 120 fpm at the working sash height with an optimum level of 100 fpm. 10. Constant volume bypass type hoods will be utilized. If substantial Organic Chemistry area is included, variable volume type hoods with restricted bypasses will be utilized for those spaces. In addition to fume hoods, the BSCs, flammable storage cabinets, and acid storage cabinets will be served as follows: a. Class II,Type A BSC- no exhaust required but an exhaust air thimble application can be used for a Class II, Type A. The exhaust air outlets from a Class II, Type B1, B2, B3, and Class III BSCs shall be connected to the building exhaust air system. b. Flammable storage cabinets and acid storage cabinets will be ventilated utilizing a 2" galvanized pipe directly connected from the cabinet to the fume exhaust ductwork. An exhaust air valve will not be utilized for the cabinet. (Note: Some of the Class II Type B2 BSCs will utilize bag-in/bag-out 99.97 percent HEPA filters within the BSC cabinet.) 11. Specify welded stainless steel Type 316L ductwork (18 gage minimum) for exhaust air ductwork from the BSCs, laboratory glassware washer, and chemical fume hoods where corrosive chemicals may be used. Galvanized steel can be used as the construction duct material on other general exhaust systems. 12. Exhaust systems serving Fume Hoods, and BSCs shall be separate and independent of each other. 13. Exhaust ducts used to transport air from Biological Safety Cabinets where radioisotopes are used must be labeled with the standard Caution Radiation Symbol magenta on yellow background at 20 foot intervals. Equip Biological Safety Cabinets with proper filtration components to capture potential contaminates. 14. Laboratory rooms where radioisotopes are being processed or used shall have stainless steel exhaust grilles located 6 inches above the finished floor and shall be served by a dedicated two speed exhaust fan. A radiation monitor and or wall mounted emergency button on the wall within the laboratory shall be used to switch the fan to the higher speed in case of a radioisotope spill. 15. Filter the laboratory exhaust using exhaust filter unit housings. Each filter unit housing shall have a bank of 30 percent efficient pre-filters followed by high capacity 99.97 percent HEPA filters. 16. Route the exhaust duct through the building roof at a distance of 25 feet and downwind from any outside air intake. 17. Storage rooms that contain laboratory specialty gases or liquid nitrogen stored in dewars shall be ventilated per OSHA requirements to protect personnel from accidental asphyxiation. Page 3 of 5
18. The allowable exhaust air stack height shall be minimum 10 feet above centerline height of air intake or roofline. The stack discharge air velocity shall be equal to or greater then 3000 fpm 19. Locate exhaust discharge stack where it cannot be easily reintroduced into the building outside air intakes. Refer to Design Guideline Element D3041 for additional criteria on outside air intakes. 20. When high plume exhaust fans are being considered in the design of a laboratory exhaust system, the A/E needs to place the plume heights, design airflow rates, static pressure requirement, and maximum brake horsepower requirements on the equipment schedule. 21. A/E needs to consider wind velocities and prevailing wind direction as listed in Chapter 26 in Tables 1A, 2A and 3A of ASHRAE Handbook of Fundamentals or airport weather data. 22. Instruments that control air valves shall be capable of changing the state of room pressurization, which will be dependant on current and future use of the laboratory. AIR DEVICES 1. Refer to Sound Criteria in Design Guideline Element D3002. 2. Exhaust square panel face Titus Omni directional diffusers with round necks shall be provided in open areas. Increase neck sizes for the diffuser since they are being used for exhaust air purposes. 3. Pneumatic actuated air valves shall be used to control the exhaust airflow rates from rooms, hoods, and BSCs via feed back signals from stand alone controllers and setpoints (adjustable) from the building automation system. Part 3. Special Contract Document Requirements 1. Include a single line riser drawing of the general exhaust ventilation exhaust and pressure relief systems in the Contract Documents. This shall be initially provided in the Schematic Design Submittal. Part 4. Products 1. Refer to Master Construction Specifications. 2. Evaluate energy recovery units as appropriate to the application in accordance with the latest edition of ANSI/ASHRAE/IESNA 90.1. Page 4 of 5
3. Fume Hoods, and BSCs shall have a open sash face velocity equal to or greater then 100 fpm. A proximity or occupant sensor on each hood shall reduce the open sash face velocity to 70 fpm when the workspace in front of the hood is not occupied. 4. Preferred direct drive exhaust fans shall be similar to Strobic axial fans. 5. Supplier of laboratory HVAC airflow tracking equipment Phoenix (Accel II) or TriaTek Venturi Air Valves and BACnet compatible systems shall be used to control the exhaust airflow rates from the individual room or spaces. 6. Another laboratory HVAC supplier is Tek-Air with air valves and smart lab control system the will interface with BACnet using a Mod Bus controller. Document Revision History Issue Date Revision Description Revisor 01-01-07 Initial Adoption of Element Rev. 1 Rev. 2 Rev. 3 Rev. 4 Rev. 5 Page 5 of 5