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John Alberico M.Sc., CCEP May 10, 2013

Exhaust Re-entrainment and its Effect on Building DesignOntario Association of Architects

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■ B.Sc. (Physical Geography), University of Guelph, 1985

■ M.Sc. (Physical Geography), University of Guelph, 1988

■ Canadian Certified Environmental Practitioner

■ Member of Air and Waste Management Association

John Alberico, M.Sc., CCEPProject Director / Principal

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Engineers and scientists

Focus on climate responsive design for the built environment

Clients include architects, planners, engineers & developers

Established in 1972

>320 people worldwide

Consulting in the Science of Buildings, Structures & Environment

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Offices Around the World

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Physical Resources

Model shopWind tunnels Water flume

Computer clusterMonitoring & measurementStereolithography

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Computational Resources

Numerical modeling

GIS Meteorology Plume-RT

Computational FluidDynamics (CFD)

VirtualwindTM

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Design Issues

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Exhaust Re-entrainment and its Effect on Building Design

Course Objectives

Through this course, we will teach the participants:

Fundamentals of wind flows around buildings and how it effects exhaust dispersion.

The effect of wind flows on building performance and the health and safety of the users and the neighbours.

Modelling of exhaust dispersion and the wind environment including wind tunnel testing and computer simulations and how this modelling can be used to promote safe and efficient building design.

Typical mitigation options that can be implemented by designers to ensure acceptable air quality.

Understand how this fits in with the Environmental Compliance Approval (ECA) process in Ontario.

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Exhaust Re-entrainment and its Effect on Building Design

Presentation Outline

Introduction What is Exhaust Re‐entrainment? Why is it Important in Building Design?

Assessment Process Identify Pollutant or Odour Sources of Concern Develop Design Criteria Determine Impacts through Dispersion Modelling Develop Mitigation Measures (if Design Criteria not Met)

What is the Environmental Permitting Process in Ontario?

Questions?

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1000km

Regional State City Masterplan / Community Building Scale

100km 10km 1km 100m 10m

Air Temperature Humidity Solar Wind Air Quality Noise

Scales

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“What is Exhaust Re-entrainment?”

Many exhausts can contain toxic pollutants or strong odours.

It refers to entry or re‐entry of exhausts into a building that can lead to indoor air quality problems (protect worker’s health)

Also includes impacts on outside locations without re‐entry into the building (e.g., exposure of workers on roofs)“Self‐Contamination”

Exhausts can also impact off‐site locations“Cross‐Contamination”

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Exhaust Re-entrainment

Air Intakes

Exhaust

WIND

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Exhaust Re-entrainment “Self Contamination”

Exhaust is being drawn into the wake of the building where the

air intakes and operable windows are located.

Exhausts

Operable Window

Air Intake

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Exhaust Re-entrainment “Cross Contamination”

Staff on Roof

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“Why is it Important in Building Design?”

Ensure the well being and safety of workers and neighbours

Avoid liability from health impacts

Avoid odour complaints

Minimize lost work time

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The Assessment Process

Identify Pollutant or Odour Sources of Concern

Develop Design Criteria

Determine Impacts through Dispersion Modelling

Develop Mitigation Measures (if Design Criteria not Met)

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Common Problematic Sources

Laboratory exhausts Fume hoods Radioisotope hoods Bio‐safety hoods/cabinets Pharmacy

Combustion sources Boilers Emergency generators (gas and diesel) Vehicles using loading docks & parking garages Road traffic

Cooling towers

Building exhausts (e.g., kitchen grease hoods)

Emissions from neighbours

Any exhaust that emits a pollutant or odour to the outside

Some examples…

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Laboratory and Fume Hood Exhausts

Solid Screen wall that is bad for air movement

Poor design as air intake is too close

Exhaust emitted from stacks with downward motion

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Fume Hood Exhausts with Rain Caps

Air Intake

Exhausts

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Better performance from these stacks but aesthetic consideration

Laboratory and Fume Hood Exhausts

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Diesel Generators: Source of Pollutants & Strong Odours

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Cooling Towers

■ Re‐entrainment of biocides & scaling inhibitors

■ Moisture Loading

■ Legionella

Intakes

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Pollutant & Diesel Odour Emissions from Idling Trucks in Confined Spaces

Loading Docks

Operable Window

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Odours at Nearby Intakes (can persist for large distances)

Idling Helicopters

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Design Criteria

Safety (Health)

Odour (Annoyance)

Lethal

Toxic

Carcinogenic

The design criteria depend on the emissions rates of pollutants and odours, and the corresponding health limits and odour thresholds.

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Design Criteria: Major Types of Health Limits

Occupational

healthy workers (e.g., MOL, OSHA)

Ambient

general population (e.g., MOE, US EPA)

Emergency response (e.g., IDLH)

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Design Criteria: Examples

Exhaust Type Basis of Criterion Dilution Target

Laboratory Fume Hood Health & Odour 3,000:1

Boiler Health Typically <500:1

Diesel Generator & Diesel Truck

HealthOdour

Typically <500:1

4,000:1

Cooling Tower Health & Odour 20:1

Kitchen Odour 600:1

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Determining Health-Based Criteria: Combustion Sources

Boilers, generators and vehicles

Emissions of concern: NOx, CO, SO2 and PM

Emissions determined through manufacturer’s specifications, stack testing, engineering calculations or published data

Based on the pollutant with the highest ratio of high emission and low air quality standard

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Limiting Pollutant for Combustion Sources

PollutantSource Conc.

(ug/m3)Criterion(ug/m3)

Dilution Target

NOx 620,000 500 1,240:1

SO2 104,000 830 125:1

CO 243,000 6,000 41:1

PM 37,000 100 375:1

Limiting Pollutant ‐ NOX 1,240:1

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Determining Odour Criteria

Published odour thresholds

Ontario Ministry of the Environment

Published Journal Articles

AIHA

Odour panel tests

Where do the Criteria Come From?

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Determining Odour Criteria: Take Odour Samples

Odour Sample being taken from an Idling Diesel Truck

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Determining Odour Criteria: Conduct Odour Panel Tests

Panellist Inhaling from Sniff Tubes during an Odour Panel Test

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Determining Odour Criteria: Create Odour Response Curves

100100010000100000

Dilution Ratio

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25

50

75

100

Percen

t Pan

el R

esponse

Detection Data

Regression (Detection)

Annoyance Data

Regression (Annoyance)

Regression

Results Detection Annoyancea 3.17 3.34b 11.05 10.42

OTV 3048 1315

Odour detection and annoyance thresholds established based on odour response curves (1 OU = 50% detection)

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Determine Impacts

What Can be Done?

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Four Assessment Levels

Field Tests

Design Consultation

Numerical Modelling

Wind Tunnel Modelling

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Field Tests

Excellent visuals

Provides results for limited wind conditions that may not be worst case

Not useful for design of new buildings

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Design Consultation

Based on past experience

“Red flag” potential problems

Save headaches later

Fast turnaround

Inexpensive

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Goals:

Locate air intakes to use building massing for protection

Extend exhausts above highest roof level

Locate exhausts and intakes to take advantage of prevailing winds

Mitigation Scheme 1 Mitigation Scheme 2

Design Consultation

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Numerical Modelling: Computer Models

Z1 Roof Recirculation Region

Z2 High Turbulence Region

Z3 Roof Wake Boundary

Undisturbed Flow

Building Wake Recirculation Region

Conservative estimate of air and exhaust flow behaviour around buildings

Simple terrain and buildings

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Numerical Modelling: Computational Fluid Dynamics

Useful for more complex situations (e.g., emissions that have densities higher than air such as water droplets)

Computer Intensive

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Most Accurate and reliable

Fine-Tuning Designs

Includes Design Detail

Complex Geometry

Wind Direction

Exhaust Stack

Modeled Air Flow

Tracer

Gas

Air

Intake

Pump

Gas

Analyzer

PC

Results

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Develop Mitigation

How does building shape and massing affect exhaust dispersion?

What are practical solutions to minimize air quality impacts?

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Building Massing

Squat Building Tall Building

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Building with a Roof Step

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Building with a Roof Step

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Buildings with Different Roof Shapes

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Increase Stack Heights

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Low Stack Within Separation Bubble

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Tall Stack Outside Separation Bubble

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Effective Stack Height (HS)

HS

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Change Stack Location

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Consider Wind Frequency

0%

6%

12%

18%N NNE NE ENE E ESE SE SSE S

SSW

SW

WSW

W WNW

NW

NNW

Optimal placement of stacks to reduce entrainment based on wind frequency.

N

W E

S

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Increase Exit Velocity

Upper limit 3,000 to 4,000 fpm due to noise impacts (generators are the exception)

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Exit Velocity (W) vs. Wind Speed (U)

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Velocity (Feet per Minute)0 1000 2000 3000 4000

Per

cent

of T

ime

(%)

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10

20

30

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60

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80

90

100

Chicago

Los Angeles

Toronto

Boston

Wind Speed Distribution at 30 ft

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Manifold or Increase Flow Rate

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Manifold or Increase Flow Rate

Internal Dilution (Fume Hood Exhaust)

Spill scenario evaluation considers one spill at a time in only one fume hood

Other fume hood exhausts relatively clean and dilute the exhaust from the fume hood with the spill

Fume Hood

Fume Hood

Fume Hood

Fume Hood

with Spill

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Optimally Place Intake

Move intake location especially to side of building, but away from grade or low-level sources.

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Use Porous Screens

Solid screen walls can cause plume downwash

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Building with a Screen

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Use Porous Screens

Porous screen walls allow some flow through

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Case Study, Toronto Rail Lands – Issues

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Case Study, Toronto Rail Lands – Issues

New construction along major transportation routes and near industries in downtown Toronto

Air quality concerns with respect to emissions from the routes and industry

City of Toronto requires Air Quality Impact assessments, which includes the impact of the environment on the new construction and vice versa

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Case Study, Toronto Rail Lands – Solutions

Avoid intakes facing major transportation (rail corridor, Gardiner Expressway)

Place intakes high up or in protected areas such as courtyards

Positively pressurize building to create a net flow outward to minimize infiltration of dust and odours into units

Install high efficient particulate filters on intakes

Install controls on intakes to shut down when high CO or NOX levels occur

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Other Mitigation Options

Emission controls (low NOx burners, low sulfur fuel oil, scrubbers, selective catalytic reduction)

Operational measures (e.g., reduce operations and emissions under certain wind conditions, no idling policy, turn off intakes)

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What is a Environmental Compliance Approval (ECA)?

A legal document issued by the Ontario Ministry of Environment (MOE) that permits a facility to operate equipment that emits contaminants to the environment.

Replaced the Certificate of Approval on October 31, 2011

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When Do You Require an ECA?

Under the Environmental Protection Act (EPA), if you are a facility and you plan to:

Construct, alter, extend or replace any building, structure, equipment, or thing that may discharge a contaminant into the environment other than water; or

Alter a process or rate of production that may alter the rate of discharge of a contaminant.

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What is a Contaminant?

“…any solid, liquid, gas, odour, heat, sound, vibration, radiation, or combination of any of them resulting directly or indirectly from human activity that causes or may cause an adverse effect.”

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Environmental Compliance Process

EASRStandard Processes / Equipment

Online Registration

ECAUnique / More

Complex Processes / Facilities

Online Environmental Compliance Approval

Two Compliance Methods in Ontario: Environmental Activity and Sector Registry (EASR) Environmental Compliance Approval (ECA)

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Environmental Activity and Sector Registry (EASR)

Online application for immediate permits

Only applies to standby power systems, heating systems, automotive paint booths

Requirements noted in Ontario Regulation 245/11

Eligibility and operating requirements include size of units, noise requirements, etc.

Must register eligible activities / sectors or request Director’s order under s.20.18 to include in ECA

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Four new activities / sectors under review

Waste collection and transport by truck

Ready mix concrete manufacturing

Concrete product manufacturing

Digital printing

Next Round is to include:

Fume hoods

Small Gensets used for peak shaving

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ECA Process for Air Quality and Noise

DocumentSite

Conditions

PhysicalInventory

EmissionInventory

ImpactAssessmentusing Modelling

ComplianceAssessment

Administration, ESDM and AA Reports, & ECA Application

Refinement & Mitigation Process

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Ontario Regulation 419/05

Air quality standards apply to facility contribution only, even if other sources are nearby.

Same standards apply in both pristine and polluted environments.

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Noise Guideline Limits in Ontario

Continuous noise limits are the HIGHER of:

Minimum limits in the table below or

Measured background sound levels or

Modelled traffic noise.

One Hour Leq (dBA) or LLM (dBAI)

Time of Day Class I: Urban Class 2: Urban Class 3: Rural

0700 – 1900 50 50 45

1900 – 2300 47 45 40

2300 – 0700 45 45 40

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Typical Air & Noise Sources

Mechanical & Ventilation Systems Air makeup units/heaters Chillers or cooling towers Boilers Emergency generator Incinerator

Workshops Dust collectors Paint spray booths Welding exhausts Grinder exhausts Plasma cutters

Labs Fume hoods Specialty hoods

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Mass balance

Engineering estimates

Published emission factors

Manufacturer’s specs

Stack testing

Sound power levels

QUANTIFY AIR EMISSIONS

QUANTIFY NOISE EMISSIONS

Emissions Inventory

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Options in Case of Non-Compliance

Step 1: Refine Assessment Emission Rates and Operating Scenarios

Dispersion Models and Supporting Data

Step 2: Develop Mitigation Strategies Engineering Controls

Process or Operational Changes

Improved Dispersion

Step 3: Request for Alternative Air Standard

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Plan Ahead

Develop mitigation strategies early, if needed. Design reviews for planned changes and expansions. Conduct dispersion modelling assessments with

refined models. Saves time and money!

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ConstructionConstruction Documents

Design Development

Schematic Design

Conceptual Design

Pre‐concept Design

Post‐occupancy

Plan Ahead - Benefits of Early Design Involvement

The best time to consider air quality and noise impacts is as early as possible when problems can be identified and

corrective action can be easily incorporated.

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Questions?

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