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1-13
Establishing Appropriate Airflow Rates for
Laboratories and Chemical Fume Hoods
During Energy Reduction Projects
Exposure Control Technologies, Inc.
Thomas C. Smith 919-319-4290
Laboratory Hood Products, LLC
LabHoodPro™
1-13
Learning Objectives
Correctly apply the various standards affecting design and operation of laboratory systems
Meet the energy conservation requirements applicable to laboratory ventilation in ASHRAE Standard 90 and related documents.
Recognize the energy conservation opportunities opened by revisions in the Z9.5 Laboratory Ventilation requirements.
Satisfy the increasingly specific requirements for active management and long-term monitoring.
Apply the principles of biosafety to ventilation system design.
Relate the varying mechanical requirements to the corresponding levels of biological hazard.
ASHRAE is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to ASHRAE Records for AIA members. Certificates of Completion for non-AIA members are available on request. This program is registered with the AIA/ASHRAE for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
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Introduction & Objectives
Types of Laboratories
Types of Fume Hoods
Cost of Ventilation
ANSI/AIHA Z9.5 Ventilation Standard
Airflow Specifications
– Fume Hoods
– Labs
– Systems
Lab Ventilation Management
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• Chemical and Rad Labs
• Biology Labs (BSL 2-4)
• Nanotechnology Labs
• Animal Vivariums
• Clean Rooms
• Isolation Suites
Labs & Critical Control Environments
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• Safe
• Productive (Flexible)
• Dependable
• Energy Efficient
• Sustainable
High Performance Laboratories
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Potential for Adverse Health Effects
Inhalation
Airborne Hazard
Generation Rate
Source to Receptor
Concentration & Dose
Physical
Dermal Contact
Explosion
Dose = Concentration x Duration
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ANSI/AIHA –Z9.5 - 2012
American National Standard for Laboratory Ventilation
Published September 2012
Minimum Requirements and Best Practices
– Protect People
– Ensure Dependable Operation
– Operate Energy Efficient Labs
Requires Lab Ventilation Management Program
Specifications for New and Renovated Laboratories
– Hood Design & Operation
– Laboratory Design
– Ventilation System Design
– Commissioning and Routine Testing
– Work Practices and Training
– Preventative Maintenance
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Types of Laboratory Fume Hoods
Bench-Top
– Traditional Bypass
– Low Velocity / High Performance
– VAV – Restricted Bypass
Distillation
Floor Mounted (Walk-in)
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Fume Hood Operation and Specifications
Sash Opening Configuration
• 100% Full Open
• Design Opening
• User Opening
Average Face Velocity
• 100 fpm (0.51 m/s) – Traditional
• 60 fpm (0.3 m/s) – High Performance
Exhaust Flow
• CAV
• VAV
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Hood Monitors and VAV Flow Controls
• Hood Monitors
– Flow
– Velocity
– Pressure
• Flow Control Types
– Through the Wall Velocity
– Sash Position
– Occupancy
VAV Operating Modes
– Two State
– Full VAV
– VAV Hybrid
TTW
Velocity
Sensor
and
Hood
Monitor
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VAV Fume Hood Specifications
Qex = Vf x Af
Qex = Minimum?
Flow Reduction = Energy Reduction
Questions?
1. Average Face Velocity @ Sash Open?
2. Minimum Flow @ Sash Closed?
3. Hood Use (Demand) Sash Left Open?
60 fpm - 100 fpm
Sash Open
Sash Closed
VAV Terminal
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Minimum Flow for VAV Fume Hoods
1990s - EPA – 50 cfm / ft of Wh
2004 - NFPA 45
- 25 cfm / sq. ft. ws
- 2010 - Defers to ANSI Z9.5
2012 - ANSI Z9.5
- 150 ACH to 375 ACH
- 150 ACH ~ 10 cfm / sq. ft. ws
- 375 ACH ~ 25 cfm / sq. ft. ws
Vh
Qe
x 60 ACHh =
• Containment • Dilution • Removal
Internal Conc. (Ci)
Duct Conc. (Cd)
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Minimum Flow for VAV Fume Hoods
Effective Flow – Q’ = Qe / DF
VdC = Gdt – Q’Cdt
System Design & Operation
– VAV Flow Control
– Flow Measurement
– Duct Velocity
Hood Design
– Hood Containment
– Hood Dilution (Dilution Factor - DF)
Application
– Chemical Properties / Hazards
– Generation Rates
Ci
Ci
DF DF
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Investigate & Optimize Fume Hood Flow
Laboratory Hoods
Min. Exhaust
Flow Cfm
Min ACHh
Dilution Factor
Df
Max Gen Rate
lpm
Flow Savings
Cfm
Hood Type 1 135 164 2.95 3.3 170
Hood Type 2 127 212 1.92 3.6 75
Hood Type 3 103 165 6.6 1.5 100
Hood Type 4 130 187 2.7 3.1 130
Minimum Flow for Containment – Qmin
Minimum Flow for Dilution - ACHh
Hood Dilution Factor - DF
Max Generation Rate (25% of LEL) – Gmax
Flow Reduction from Design
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VAV Flow Response & Stability
Good Containment Intermittent
Escape
Stable vs. Unstable
Slot Velocity
Exhaust Flow
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VAV Flow Response and Stability
VAV Response To Sash Movement
0
100
200
300
400
500
600
0 10 20 30 40 50 60 70 80 90 100 110 120
Time - Seconds
Flo
w R
es
po
ns
e
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Es
ca
pe
- p
pm
Flow Response Tracer Gas - ppm
< 5 Seconds Escape
• Min and Max Flow • Response Time • Flow Stability
< 20% Variation
Sash Closed
Sash Open
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Demand for Ventilation
Hood Use & Lab Occupancy
Reduce flow and use less energy
during periods of reduced activity. 74%
26%
Occupied
Max Flow
Unoccupied
Min. Flow
Lab Time vs. Analytical Time
– Experiments in Lab
– % Hood Utilization
– Analysis in Office
Nights, Weekends, Holidays
CAV vs. VAV
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Laboratory Operating Specifications
Min and Max Flow
Offset Volume & dP
VAV Response
Conditioning Loads
ACH – Dilution
– Typical 4 ACH to 12 ACH
– Minimum with DCV?
Air Change Effectiveness
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Agency Ventilation Rate
OSHA 29 CFR Part 1910.1450 4-12 ACH
ASHRAE Lab Guides 4-12 ACH
UBC – 1997 1 cfm/ft2
IBC – 2003 1 cfm /ft2
IMC – 2003 1 cfm/ft2
U.S. EPA 4 ACH Unoccupied Lab
8 ACH Occupied Lab
AIA 4-12 ACH
NFPA-45-2004 4 ACH Unoccupied Lab
8 ACH Occupied Lab
NRC Prudent Practices 4-12 ACH
ANSI/AIHA Z9.5 ACH is not appropriate.
Rate shall be established by the owner.
ACGIH 24th Edition, 2001 Ventilation depends on the generation rate and toxicity of
the contaminant and not the size of the room.
Typical ACH Guidelines
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Emissions in Labs Requiring Dilution
Escape from Lab Hoods
Improper Bench Top Procedures
Unventilated Equipment
Fugitive Emissions
– Chemical Bottles
– Storage Containers
– Gas Cylinders
Accidental Spills
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Contaminant Concentration, ACH
& Level of Concern
Required ACH for Dilution to LOC
Material LOC
PEL, TLV
(PPM)
Gen. Rate
= 0.1 lpm
Gen. Rate
= 0.5 lpm
Gen. Rate
= 1.0 lpm
Gen. Rate
= 4 lpm
Gen. Rate
= 8 lpm
Gen. Rate
= 20 lpm
Acetone 750 0.1 0.7 1.3 5.2 10 26
Ethyl acetate 400 0.2 1.2 2.5 10 20 49
Methyl ethylketone 200 0.5 2.5 4.9 20 39 98
Toluene 100 1.0 4.9 10 39 79 196
Ammonia (STEL) 35 3 14 28 112 224 561
Acetic acid 10 10 49 98 393 785 1963
Phenol 5 20 98 196 785 1570 3926
Formaldehyde 3 33 164 327 1309 2617 6544
Carbon tetrachloride 2 49 245 491 1963 3926 9815
Chlorine 0.5 196 982 1963 7852 15705 39262
Phosgene 0.1 982 4908 9815 39262 78524 196309
Toluene diisocyanate 0.005 19,631 98,155 196,309 785,238 1,570,475 3,926,188
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Multiple Hazards
Varied Emission Scenarios
Lab Size & Configurations
Air Change Effectiveness
Accumulation & Decay at Different ACH
VdC = Gdt – Q’Cdt
Rate of Accumulation = Generation Rate – Removal Rate
C =
G 1 - e
- Q’ ∆ t
V
( )
Q’
X 10 6
Lab Dilution Calculator
1-13
Specifying Airflow Rates for Labs
Air Change Rate (ACH)?
Evaluate hazardous emissions
Use appropriate laboratory hoods
Capture hazards at the source
Ensure air change effectiveness
Base airflow rates on:
– Hood Exhaust Requirements
– IAQ Requirements
– Comfort (Temperature)
– Pressurization/Isolation
1-13
System Operating Specifications
Energy Savings Require Reducing Total Building Flow
• Max and Min Flows
• AHUs and Ex. Fans
• Static Pressure
• Duct Transport Velocity
• Exhaust Stack Discharge
• Control Capabilities
─ VAV Diversity
─ VAV Sensitivity
1-13
Laboratory Ventilation Management Program
(LVMP)
System Management and Sustainability Plan
– Organization and Responsibilities
– Effective Collaboration/Integration
– SOP’s for Testing and Maintenance
– Metrics and Monitoring
– BAS Utilization
Management of Change
Personnel Training
Required By ANSI Z9.5
Cognizant Person