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Establishing Appropriate Airflow Rates for

Laboratories and Chemical Fume Hoods

During Energy Reduction Projects

Exposure Control Technologies, Inc.

Thomas C. Smith 919-319-4290

tcsmith@labhoodpro.com

Laboratory Hood Products, LLC

LabHoodPro™

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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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Primary Objective:

Safe & Productive

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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VAV Flow Response and Stability

Sash Open

Sash Closed

VAV Terminal

Good

Bad

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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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Cost of Air Changes Per Hour

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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

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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

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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

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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

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END

QUESTIONS?

Thomas C. Smith

tcsmith@labhoodpro.com