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Principles of Laboratory Design and Fume Hood Operation Jim Hall CEO

The art of efficiency. The science of safety. TODAY’S OBJECTIVES

The ASHRAE 110 2016 Standard’s position on fume hood safety require new considerations in fume hood operation and lab design. Today’s presentation will review current lab control options and important design parameters.

TODAY’S OBJECTIVES

PRESENTATION OUTLINE

 Lab Design Parameters  History of Fume Hoods  Review of Control Strategies  Containment Testing and Performance  ASHRAE 110-2016 Standard

FUME HOOD SPECIFICATIONS

WHERE ARE FUME HOODS TYPICALLY SPECIFIED?  GENERALLY AN ARCHITECTURAL ITEM  SPECIFICATION DRIVEN BY:  ARCHITECT  INDUSTRIAL HYGIENIST  INTERIOR DECORATOR  AMERICAN INSTITUTE OF ARCHITECTS (AIA)- MASTERSPEC - SECTION 115313 – LABORATORY FUME HOODS

HOWEVER, WE KNOW THAT  CHEMICAL HOODS & THEIR OPERATION ARE CODIFIED LIFE SAFETY DEVICES  CHEMICAL HOODS ARE INTRICATE PIECES OF MECHANICAL EQUIPMENT WITH SOPHISTICATED CONTROLS  SUCCESSFUL IMPLEMENTATION REQUIRES COMPREHENSIVE SYSTEMS KNOWLEDGE

UPDATED STANDARDS FOR FACE VELOCITY

 FACE VELOCITY HAS BEEN USED AS THE PRIMARY INDICATOR OF LABORATORY HOOD PERFORMANCE FOR SEVERAL DECADES.

 FACE VELOCITY SHALL BE ADEQUATE TO PROVIDE CONTAINMENT. FACE VELOCITY NOT A MEASURE OF SAFETY. (SEFA 1-2002 SECTION 4.3.1 & 5.3.4)

 “METHOD OF TESTING THE PERFORMANCE OF LABORATORY FUME HOODS” (ASHRAE 110 CONTAINMENT BASED TEST) REVEALS THAT THE FACE VELOCITY IS ACTUALLY AN INADEQUATE INDICATOR OF HOOD PERFORMANCE.

 HOODS WITH EXCELLENT CONTAINMENT CHARACTERISTICS MAY OPERATE ADEQUATELY BELOW 80 FPM WHILE OTHERS MAY REQUIRE HIGHER FACE VELOCITIES. IT IS, THEREFORE, INAPPROPRIATE TO PRESCRIBE A RANGE OF ACCEPTABLE FACE VELOCITIES FOR ALL HOODS.

 THE AVERAGE FACE VELOCITY ALONE IS INADEQUATE TO DESCRIBE HOOD PERFORMANCE REFERENCE ANSI/AIHA Z9.5-2012 CHALLENGE TO THE STANDARD THINKING

 FUME HOODS USE SIGNIFICANT ENERGY  FUME HOODS ARE LIFE SAFETY EQUIPMENT  BALANCING SAFETY AND ENERGY IS A CHALLENGE  FUME HOODS ARE A CRITICAL COMPONENT OF THE MECHANICAL SYSTEM  FUME HOODS COME IN A WIDE VARIETY OF SPECIFICATIONS AND PERFORMANCE  WHEN PROPERLY CONSIDERED, FUME HOODS CAN HAVE A SIGNIFICANT IMPACT ON THE ENTIRE BUILDING DESIGN, ENERGY AND SAFETY OF A LAB PROJECT  Therefore, FUME HOODS SHOULD BE PART OF THE MECHANICAL SPECIFICATION and considered as an important piece of the mechanical design

Critical Lab Design Parameters

• SAFETY – Occupant safety at fume hood and room level. – Accurate measurement that reliably responds to changes and restores safe set points. – Face Velocity of hoods must be measured and exhaust systems modulated rapidly to hold defined set points. – Rapid restoration to safe set points for fume and pathogen containment to prevent roll-outs or containment breaches.

• CONTAINMENT – Removal of airborne substances, fumes and contaminants. – Labs and Isolation Rooms must have supply/make up air systems which can track the total exhaust for each area or zone to achieve proper air balance and minimum air change per hour specifications while maintaining predetermined room air static pressure.

Once safety parameters are defined, it is recommended to use a Closed Loop Control in order to reach and hold safety set points effectively

Secondary Lab Design Parameters

STABILITY – Accurate measurement that reliably responds to changes and restores safe set points. – Vacillations of less than 5% from desired set point (or as determined by engineer/TAB) to ensure that the system is measuring relatively stable and actual airflow

COMFORT – Effective temperature and humidity control.

FLEXIBILITY AND SCALABILITY – Adaptation to a variety of technologies. – Adjustability to meet site design specification and regulatory requirements as well as modifications to environment.

Laboratory Containment

Reduce or eliminate exposure of laboratory workers, other persons, and the outside environment to potentially hazardous agents! Primary Containment: Protection of personnel and the immediate laboratory environment from exposure to infectious agents. Achieved through a combination of appropriate selection and operation of safety equipment. Hood level. Secondary Containment: Protection of the environment external to the laboratory from exposure to infectious materials. Achieved through a combination of facility design and operational practices. Room level. Laboratory Containment

Proper fume hood face velocity control impacts overall lab air control.

Good system design must accommodate the strong interrelationship between the laboratory air supply and the large and varying air supply demands created by fume hood operation

 A lab equipped with fume hoods must design the supply airflow capacity with a substantial  increase over that of conventional HVAC design for the same size space.  Larger supply airflow is needed to provide the airflow required by the fume hoods when in use.

 General exhaust flow capacity is not necessarily increased for the lab with fume hoods.

 Temperature control is secondary to airflow control needed for meeting fume hood needs.

 Supply air control must be designed to enable the airflow rate to be modulated in response  to the varying demands of fume hood activity.  Airflow variations will frequently be in the order of several hundred CFM to several thousand CFM  in labs containing multiple fume hoods.  Changes are sudden and may be large, requires control that is different from conventional rooms.  Control must be capable of adjusting the supply airflow requirements substantially and  quickly, to ensure the safety of personnel who are using fume hoods.

Laboratory Containment

There are three separate control systems that make up the overall control system in a variable volume laboratory:

A control system for each fume hood to control the flow into the fume hood to assure capture and containment by the fume hood (to maintain a constant sash opening velocity).

A control system for the bypass air damper on the exhaust fan system to ensure sufficient velocity through the exhaust stack.

A room ventilation control system which maintains; room pressurization, a minimum number of air changes, and comfort levels within the laboratory. LAB DESIGN POSSIBILITIES

NEW CONSTRUCTION RETROFIT OF EXISTING LAB EXPANSION OF EXISTING LAB REDESIGN OF EXISTING LAB

DESIGN DRIVERS

PRIORITIES MAY VARY DEPENDING ON PROJECT SAFETY IS ALWAYS PARAMOUNT BUDGET ENERGY USAGE CAPACITY OF SYSTEMS CODE COMPLIANCE

LAB CONSTRUCTION OPTIONS

DEPENDING ON OWNER NEEDS CAN INCLUDE: NEW LAB CONSTRUCTION IN-SITU RETROFIT OF MECHANICAL LEAVE MECHANICAL SYSTEMS IN PLACE UPGRADE FROM ANALOG TO DIGITAL CONTROLS ADDITION OF Fume Hood controls IN-SITU RETROFIT OF FUME HOODS CONVERSION TO LOW FLOW HIGH PERFORMANCE TO INCREASE CAPACITY GRANDFATHERED BUILDINGS

BRIEF HISTORY OF THE FUME HOOD BASIC FUME HOOD OPERATION

EXTENSION OF MECHANICAL DUCTWORK (PROPER DESIGN AND SYSTEM CONSIDERATION ARE CRITICAL FOR SUCCESS) APPLICABLE AIRFLOW FUNDAMENTALS

VELOCITY PRESSURE ENERGY AVAILABLE IN FUME HOODS

FUME HOOD FACE VELOCITY – VELOCITY PRESSURE

 120 fpm - 0.000898 in. of w.c.  100 fpm - 0.000623 in. of w.c.  80 fpm - 0.000399 of w.c.

FUME HOOD FACE VELOCITY EXPRESSED AS MPH

 120 fpm - 1.36 mph  100 fpm - 1.13 mph  80 fpm - 0.91 mph APPLICABLE AIRFLOW FUNDAMENTALS

• Dynamic changes in sash position can cause fumes to spill from the fume hood.

• Turbulence can bring contaminants back into the user's breathing zone.

• Too low a velocity: the hood will not be capable of containing generated fumes.

• Too high and turbulent: can cause fumes to escape.

• Turbulent events include: – operator movement – blockages of the fume hood opening – air diffusion patterns – pedestrian traffic in front of the hood – room static pressure changes – duct static pressure challenges – fan failures – air distribution – thermal convection – container storage within the hood – poor air register placement – discharge that produces a shear flow – disruptive supply terminal velocity

HOOD FAILURE - SPILLAGE

TYPICAL LOCATION OF HOOD SPILL IS AT SASH HANDLE

HOOD SPILLS WHEN VORTEX COLLAPSES! HOOD FAILURE - SPILLAGE

CONTAINMENT TEST W/ LP MSV HOOD: SF6 TRACER GAS @ 100 FPM FACE VELOCITY CASE 1: PROPER USE CASE 2: ADVERSE USE CASE3: ADVERSE USE  EQUIPMENT 6” FROM  EQUIPMENT 1” FROM  EQUIPMENT 1” FROM SASH SASH SASH  EQUIPMENT RAISED  EQUIPMENT RAISED  EQUIPMENT ON WORK SURFACE CFD CONTAINMENT MODELING

CONTAINMENT = SAFETY 51 FPM FACE VELOCITY 0 PPM LEAKAGE BY CFD AND EMPIRICAL TEST CFD CONTAINMENT MODELING

CONTAINMENT = SAFETY 51 FPM FACE VELOCITY 0 PPM LEAKAGE BY CFD AND EMPIRICAL TEST NOTION OF HOOD PERFORMANCE

SCIENTIFIC APPARATUS MAKER ASSOCIATION (SAMA) STANDARD FOR LABORATORY FUME HOODS (NOW KNOWN AS THE LABORATORY PRODUCTS ASSOCIATION)

 5.1.3 SPECIFIC MATERIALS THAT ARE TO BE USED IN THE FUME HOODS WHICH MAY AFFECT FACE VELOCITY. LIGHT WEIGHT POWDERS THAT HAVE NO TOXICITY HAZARD MAY DICTATE VERY LOW FACE VELOCITIES. KYMOGRAPH HOODS ALSO REQUIRE VERY LOW VELOCITIES. HOODS USED TO HOUSE LABORATORY TYPE MACHINE TOOLS , GRINDERS OR CENTRIFUGES MAY REQUIRE HIGHER FACE VELOCITIES THAN TOXICITY LEVELS MIGHT DICTATE.

 5.2 FACE VELOCITY GUIDE. FACE VELOCITIES OF LABORATORY FUME HOODS MAY BE ESTABLISHED ON THE BASIS OF THE TOXICITY OR HAZARD OF THE MATERIALS USED OR THE OPERATIONS CONDUCTED WITHIN THE FUME HOOD. A SUGGESTED GUIDE FOR DETERMINING FACE VELOCITIES THAT MAY BE SUITABLE FOR LABORATORY FUME HOODS IS AS FOLLOWS:

 5.2.1 CLASS A FUME HOODS. FUME HOODS IN THIS CLASSIFICATION ARE USED FOR MATERIALS OF EXTREME TOXICITY OR HAZARD SUCH AS TETRAETHYL LEAD, BERYLLIUM COMPOUNDS, METAL CARBONYLS AND VOLATILE CARCINOGENS. THE RECOMMENDATIONS FOR AVERAGE VELOCITY AT THE FACE OF THE FUME HOOD IS 125 TO 150 FEET PER MINUTE (38.1M/MIN TO 45.7 M/MIN) (.64M/S TO .76M/S) WITH THE CORRESPONDING MINIMUMS AT ANY ONE POINT 100 TO 125 FEET PER MINUTE (30.48 M/MIN TO 38.1 M/MIN) (.51M/S TO .64 M/S).

 5.2.2 CLASS B FUME HOODS. FUME HOODS IN THIS CLASSIFICATION ARE USED FOR MOST MATERIALS AND OPERATIONS IN THE LABORATORY. THE RECOMMENDATION FOR AVERAGE VELOCITY AT THE FACE OF THE FUME HOOD IS 100 FEET PER MINUTE (30.48 M/MIN) (.51 M/S), WITH A MINIMUM AT ANY ONE POINT OF 80 FEET PER MINUTE (24.4 M/MIN), (.41 M/S).

 5.2.3 CLASS C FUME HOODS. FUME HOODS IN THIS CLASSIFICATION ARE USED FOR MATERIALS OR OPERATIONS WHERE THE HAZARD IS NOT HIGH. CLASS C FUME HOODS MAY BE USED FOR LOW TOXICITY MATERIALS SUCH AS ACETONE, ETHANOL AND STRAIGHT-CHAIN HYDROCARBONS, AND FOR OPERATIONS CREATING NUISANCE DUSTS AND FUMES. THE RECOMMENDATIONS FOR AVERAGE VELOCITY AT THE FACE OF THE FUME HOOD RANGE FROM 75 TO 80 FEET PER MINUTE (22.9 M/MIN TO 24.4 M/MIN) (.38 M/S TO .41 M/S). WITH CORRESPONDING MINIMUMS AT ANY ONE POINT OF 50TO 60 FEET PER MINUTE (15.24 M/MIN TO 18.3 M/MIN) (.25 M/S TO .31 M/S). NOTION OF HOOD PERFORMANCE

ASHRAE HVAC APPLICATION HANDBOOK 1999 & 2003 EDITION COMPARISON

TYPICAL SYSTEM PARAMETERS

 DESIGN FOR LIFE SAFETY AND CODE COMPLIANCE  PARADIGMS  VARIABLE-AIR-VOLUME (VAV)  CONSTANT-AIR-VOLUME (CAV)  HIGH PERFORMANCE  EXHAUST AND SUPPLY CAPACITY  TURNDOWN / SETBACK  SYSTEM STABILITY & RESPONSE TIME  SUPPLY DIFFUSER (LOCATION)  EXHAUST DUCTWORK CONFIGURATION  DIVERSITY (MORE LATER)  INITIAL/ONGOING COMMISSIONING  LAB PROGRAMMING & FUNCTION  STANDARD OPERATING PROCEDURE  LIFE-CYCLE COSTING / ENERGY USAGE TYPICAL LABORATORY ANATOMY FUNDAMENTAL CONTROL STRATEGIES SYSTEM ARCHITECTURE

VARIABLE AIR VOLUME CONSTANT AIR VOLUME

FUNDAMENTAL CONTROL STRATEGIES

COMMON COMPONENTS  SAFETY MONITOR  FLOW/VELOCITY SENSING TECHNOLOGY  EXHAUST SYSTEM  SUPPLY/MAKE-UP AIR SYSTEM

VARIABLE AIR VOLUME  VFD  CONTROL OUTPUT (SASH POSITION/OCCUPANCY SENSOR)  VAV EXHAUST VALVE W/ ACTUATOR  VAV SUPPLY VALVE W/ ACTUATOR  ROUTERS/GATEWAYS  SYSTEM CONTROLLER

CONSTANT AIR VOLUME  BALANCING DAMPER  2 POSITION STRATEGY  TO TAKE ADVANTAGE OF MINIMUM HOOD AIRFLOWS PER NFPA  VFD OR BYPASS PLENUM  2 POSITION ACTUATORS  CONTROLLER FUNDAMENTAL CONTROL STRATEGIES VARIABLE AIR VOLUME (VAV) BASIC PRINCIPLES

SUPPLY TEMPERATURE IS CONSTANT AND AIR VOLUME IS VARIED TO CONTROL SPACE CONDITION

EXHAUST VOLUME VARIES TO MEET VENTILATION DEMAND

FUME HOOD EXHAUST VOLUME VARIES BASED ON FACE VELOCITY

FUME HOOD REVERTS TO MINIMUM ACCEPTABLE FLOWS BASED ON OPERATOR PRESENCE/SASH POSITION HOOD LEVEL CONTAINMENT

Options  Sash Sensing  Velocity Sensing  Sash Sensing with Velocity Sensing  Constant Volume Venturi Valve  Venturi Valve with Electronic Actuation  Venturi Valve with Pneumatic Actuation ROOM LEVEL CONTAINMENT

 Constant Volume Venturi Valves at the Hood and/or Room Level  Fixed Volume Offset with Venturi Valve at the Room Level  Pressure Monitoring/Control at the Room Level  Sash Sensing with Room Level Volumetric Offset  Sash Sensing with Velocity Sensor Safety Override  at the Hood and Room Level Volumetric Offset  Velocity Sensor Safety Override at Both the Hood  and the Room Level  Sash Sensing with Velocity Safety Override  at Both the Hood and the Room Level FUNDAMENTAL CONTROL STRATEGIES CONSTANT AIR VOLUME (CAV) BASIC PRINCIPLES

SUPPLY AIR VOLUME REMAINS CONSTANT AND TEMPERATURE VARIES TO CONTROL SPACE CONDITIONS

VENTILATION DEMAND IS HANDLED BY CONSTANT EXHAUST VOLUMES TWO-POSITION/SET BACK STRATEGIES OFTEN EMPLOYED

FUME HOOD EXHAUST VOLUME IS CONSTANT FUME HOODS CAN BE BYPASS TYPE AUXILIARY AIR TYPE HIGH PERFORMANCE FUNDAMENTAL CONTROL STRATEGIES CAV WITH VARIABLE FACE VELOCITY (VFV) Variable Face Velocity

Available on Low Flow High Performance Hoods VENTILATION DEMAND IS HANDLED BY CONSTANT EXHAUST VOLUMES TWO-POSITION/SET BACK STRATEGIES OFTEN EMPLOYED FUME HOOD EXHAUST VOLUME IS CONSTANT MEASURING AND MAINTAINING A STABLE VORTEX RATHER THAN CONTROLING TO FACE VELOCITY NO LONGER MEASURING OR CONTROLLING TO FACE VELOCITY CONSTANT VOLUME WITH VFV STABILIZED VORTEX

 HENRI COANDA SHOWED THAT A STABLE VORTEX REMAINS STATIONARY ON TWO OR MORE OPPOSING SURFACES AND IS FULLY DEVELOPED EVEN WITH TURBULENCE ON ONE OF IT’S CONTROLLING JET STREAMS

 A STABLE VORTEX HAS MEMORY AND MOMENTUM

CONSTANT VOLUME WITH VFV

STABILIZED VORTEX = CONTAINMENT

CONSTANT VOLUME EXHAUST

STABLE VORTEX VFV CONTROLLER

VFV-C LO PRESS DROP LINEAR DAMPER

AIRFLOW PROBE

VORTEX

ALARM VANVURI VALVE ACTUATOR

TOTAL PRESS VORTEX SENSOR

CONSTANT VOLUME VENTURI VALVE (ROOM AIR)

R NEW - STABLE VORTEX FUME HOOD DATE: 07/2009 CONSTANT VOLUME WITH VFV

STABLE VORTEX AT MULTIPLE SASH POSITIONS

CV CV CV

Stable Vortex Stable Vortex Stable Vortex VFV Controller VFV Controller VFV Controller

Lo Press Drop VFV-C VFV-C Lo Press Drop VFV-C Lo Press Drop Linear Damper Linear Damper Linear Damper

Airflow Airflow Airflow Probe Probe Probe

Vanvuri Valve Vanvuri Valve Vanvuri Valve Total Press Actuator Total Press Actuator Total Press Actuator Vortex Sensor Vortex Sensor Vortex Sensor

Venturi Venturi Venturi Valve Valve Valve CV

CV

CV

Sash Full Open Sash Half Open Sash Fully Closed (Venturi Valve Full Open) (Venturi Valve Partially Closed) (Venturi Valve 90% Closed)

New - Stable VortexR Fume Hood DATE: 07/2009 APPLICABLE CODES & STANDARDS

 NFPA – 45 STANDARD ON FIRE PROTECTION FOR LABORATORIES USING CHEMICALS – 2015 EDITION  NFPA – 30 FLAMMABLE AND COMBUSTIBLE LIQUIDS CODE – 2015 EDITION  OSHA - CODE OF FEDERAL REGULATIONS (CFR) TITLE 29, LABOR, PART 1910 – REVISED JULY 2016 §1910.1450 OCCUPATIONAL EXPOSURE TO HAZARDOUS CHEMICALS IN LABORATORIES  ANSI/AIHA z9.2 – 2012 FUNDAMENTALS GOVERNING THE DESIGN AND OPERATION OF LOCAL EXHAUST VENTILATION SYSTEMS  ANSI/AIHA z9.5 – 2012 LABORATORY VENTILATION § 3.3.1 Face Velocity and 3.3.2 Laboratory Hood Minimum Flow Rate  ASHRAE HANDBOOK - HVAC APPLICATIONS  ASHRAE STANDARD 110 - 2016 METHOD OF TESTING PERFORMANCE OF LABORATORY HOODS PERFORMANCE TESTING

ASHRAE STANDARD 110 – 2016 METHOD OF TESTING PERFORMANCE OF LABORATORY HOODS PERFORMANCE TESTING

SCOPE METHOD APPLIES TO CONVENTIONAL, BYPASS, AUXILIARY AIR, AND VARIABLE AIR VOLUME LABORATORY FUME HOODS

THE METHOD CONSISTS OF THE FOLLOWING TESTS 1. FLOW VISUALIZATION 2. FACE VELOCITY MEASUREMENTS 3. TRACER GAS CONTAINMENT

WHAT IS NOT DESCRIBED IN THE STANDARD (BUT CRITICAL) 1. CROSS-DRAFTS 2. WORK PROCEDURES 3. INTERNAL OBSTRUCTIONS 4. THE PROCEDURE BEING PERFORMED 5. THERMAL CHALLENGE 6. RATE OF RESPONSE PERFORMANCE TESTING - CONTAINMENT

PERFORMANCE RATING

A RATING DESIGNATED BY A SERIES OF LETTERS AND NUMBERS CONSISTING OF THE LETTERS AM, AI, OR AU AND A TWO- OR THREE-DIGIT NUMBER:

 AM yyy  AI yyy  AU yyy

WHERE:  AM IDENTIFIES AN “AS MANUFACTURED” TEST  THE LABORATORY HOOD IS BUILT AND ASSEMBLED BY THE MANUFACTURER AND TESTING IS PERFORMED AT THE FACTORY.  AI IDENTIFIES AN “AS INSTALLED” TEST  THE LABORATORY HOOD IS INSTALLED AT THE LOCATION OF THE CUSTOMER. THE HOOD IS TESTED EMPTY, BUT WITH THE VENTILATION SYSTEM IN THE INSTALLATION BALANCED AND THE HOOD IN ITS FINAL LOCATION.  AU IDENTIFIES AN “AS USED” AND TEST  THE TEST IS CONDUCTED AFTER THE HOOD HAS BEEN INSTALLED AND USED BY THE CHEMIST. THE TYPICAL EQUIPMENT REMAINS IN THE HOOD AND OTHER ACTIVITIES IN THE LABORATORY CONTINUE.  YYY IS THE CONTROL LEVEL OF TRACER GAS ESTABLISHED BY THE TEST IN PPM PERFORMANCE TESTING - CONTAINMENT

SASH PERFORMANCE RATING

A RATING DESIGNATED BY A SERIES OF LETTERS AND NUMBERS CONSISTING OF THE LETTERS SME-AM, SME- AI, OR SME-AU AND A TWO- OR THREE-DIGIT NUMBER:

 SME-AM yyy  SME-AI yyy  SME-AU yyy

WHERE:  SME MEANS “SASH MOVEMENT EFFECT  THE MAXIMUM 45-SECOND ROLLING AVERAGE OF THE POSITIONAL TRACER GAS CONCENTRATION OBSERVED DURING A SERIES OF SASH MOVEMENT EFFECTS FOR ALL TESTS AT THE POSITIONS TESTED ON A CENTER OF THE HOOD OPENING.  AM IDENTIFIES AN “AS MANUFACTURED” TEST  AI IDENTIFIES AN “AS INSTALLED” TEST  AU IDENTIFIES AN “AS USED” AND TEST  YYY IS THE SASH MOVEMENT EFFECT IN PPM PERFORMANCE TESTING

IF USING THE STANDARD AS PART OF A SPECIFICATION THE FOLLOWING MUST BE SPECIFIED: 1. SASH TEST OPENING OR OPENINGS, WHICH SHOULD ADDRESS BOTH THE DESIGN OPENINGS AND TYPICAL USE OPENINGS 2. AVERAGE FACE VELOCITY 3. RANGE OF FACE VELOCITIES 4. AVERAGE FACE VELOCITY FOR SASH AT 25% AND 50% OF THE DESIGN HOOD OPENING 5. ACCEPTABLE SMOKE VISUALIZATION TESTS 6. PERFORMANCE RATING (AS DEFINED IN THE STANDARD) 7. SASH MOVEMENT PERFORMANCE RATING 8. FOR VARIABLE AIR VOLUME HOODS, THE SPEED OF RESPONSE AND TIME TO STEADY STATE  THE TIME, MEASURED FROM THE FIRST MOVEMENT OF THE SASH, FOR THE VAV SYSTEM TO RESTORE THE SLOT VELOCITY OR AIRFLOW TO 90% OF THE AVERAGE STEADY-STATE VALUE. AND TIME TO STEADY STATE  THE TIME, MEASURED FROM THE FIRST MOVEMENT OF THE SASH, FOR THE VAV SYSTEM TO RESTORE AND MAINTAIN THE AVERAGE SLOT VELOCITY OF AIRFLOW BETWEEN 90% AND 110% OF THE AVERAGE STEADY-STATE VALUE 9. FOR AUXILIARY AIR HOODS, THE PERCENTAGE OF AUXILIARY AIR SUPPLY 10. SPECIAL CONDITIONS OR TESTS CAV WITH VFV

FACE VELOCITY ALONE IS NOT AN ADEQUATE INDICATOR OF HOOD PERFORMANCE

CONTAINMENT IS ACHIEVED BY CONTROLLING / MAINTAINING A STABLE VORTEX IN THE HOOD IN RESPONSE TO STATIC AND DYNAMIC CHALLENGES

PROPER HOOD DESIGN RESULTS IN A STABLE VORTEX AT SIGNIFICANTLY LOWER AIRFLOW SUMMARY

FACE VELOCITY ALONE IS NOT AN ADEQUATE INDICATOR OF HOOD PERFORMANCE

FUME HOODS ARE AN IMPORTANT COMPONENT OF THE LAB MECHANICAL SYSTEMS

INCREASED FLEXIBILITY IN LAB DESIGN OPTIONS MEAN THE HOOD SHOULD BE CONSIDERED PART OF THE MECHANICAL SPECIFICATION

SUMMARY

 LAB SAFETY RESPONSIBILITY IS NOT SATISFIED SOLELY BY TESTING FACE VELOCITY.

 FUME HOODS WIDELY VARY IN PERFORMANCE, SPECIFICATION, AND HOW THEY ARE USED.

 FUME HOODS SHOULD BE CONSIDERED AN INTEGRAL PART OF THE MECHANICAL SYSTEM AND THE CONTROL STRATEGY.  CONSIDER ALL THE RIGHT CONTROL STRATEGIES IN CHOOSING THE BEST ONE FOR THE PROJECT NEEDS.