Ventilation for Control of the Work Environment

WILLIAM A. BURGESS is Associate Professor of Occupational Health Engineering, Emeritus, at the Harvard School of Public Health. He is the 1996 recipient of the Donald E. Cummings Memorial Award of the American Industrial Hygiene Association, and the author of Recognition of Health Hazards in Industry (Wiley). MICHAEL J. ELLENBECKER is Professor of Industrial Hygiene in the Department of Work Environment at the University of Massachusetts Lowell and the Director of the Toxics Use Reduction Institute. A Certified Industrial Hygienist, Dr. Ellenbecker received his ScD in environmental health sciences from Harvard. ROBERT D. TREITMAN, a graduate of Brown University and the Harvard School of Public Health, has done extensive research and consulting in industrial hygiene and indoor air pollution. He is currently Vice President and co-owner of Softpro, Inc., in Waltham, Massachusetts. CONTRIBUTORS-Professor Michael Flynn, University of North Carolina at Chapel Hill, has contributed a chapter introducing the application of computational methods to the study of ventilation. Martin Horowitz, an industrial hygiene pr actitioner at Analog Devices, has presented an overview of the techniques for the identification and control of contaminant reentry.

• List of Units xiiiPreface xv1 Ventilation for Control 11.1 Control Options 21.2 Ventilation for Control of Air Contaminants 31.3 Ventilation Applications 51.4 Case Studies 71.5 Summary 9References 112 Principles of Airflow 122.1 Airflow 132.2 Density 132.3 Continuity Relation 142.4 Pressure 162.4.1 Pressure Units 162.4.2 Types of Pressure 172.5 Head 182.6 Elevation 202.7 Pressure Relationships 222.7.1 Reynolds Number 242.8 Losses 262.8.1 Frictional Losses 262.8.2 Shock Losses 282.9 Losses in Fittings 302.9.1 Expansions 302.9.2 Contractions 322.9.3 Elbows 352.9.4 Branch Entries (Junctions) 362.10 Summary 38List of Symbols 38Problems 393 Airflow Measurement Techniques 433.1 Measurement of Velocity by Pitot–Static Tube 453.1.1 Pressure Measurements 473.1.2 Velocity Profile in a Duc 503.1.3 Pitot–Static Traverse 573.1.4 Application of the Pitot–Static Tube and Potential Errors 603.2 Mechanical Devices 613.2.1 Rotating Vane Anemometers 613.2.2 Deflecting Vane Anemometers (Velometer) 683.2.3 Bridled Vane Anemometers 713.3 Heated-Element Anemometers 723.4 Other Devices 753.4.1 Vortex Shedding Anemometers 753.4.2 Orifice Meters 763.4.3 Venturi Meters 763.5 Hood Static Pressure Method 773.6 Calibration of Instruments 793.7 Observation of Airflow Patterns with Visible Tracers 803.7.1 Tracer Design 813.7.2 Application of Visible Tracers 84List of Symbols 85References 86Manufacturers of Airflow Measuring Instruments 87Manufacturers of Smoke Tubes 87Problems 874 General Exhaust Ventilation 904.1 Limitations of Application 914.2 Equations for General Exhaust Ventilation 934.3 Variations in Generation Rate 994.4 Mixing 1004.5 Inlet  Outlet Locations 1014.6 Other Factors 1024.7 Comparison of General and Local Exhaust 105List of Symbols 106References 106Problems 1075 Hood Design 1085.1 Classification of Hood Types 1095.1.1 Enclosures 1095.1.2 Exterior Hoods 1105.1.3 Receiving Hoods 1155.1.4 Summary 1165.2 Design of Enclosing Hoods 1165.3 Design of Exterior Hoods 1205.3.1 Determination of Capture Velocity 1205.3.2 Determination of Hood Airflow 1255.3.3 Exterior Hood Shape and Location 1355.4 Design of Receiving Hoods 1355.4.1 Canopy Hoods for Heated Processes 1355.4.2 Hoods for Grinding Operations 1385.5 Evaluation of Hood Performance 141List of Symbols 142References 142Appendix: Exterior Hood Centerline Velocity Models 144Problems 1486 Hood Designs for Specific Applications 1516.1 Electroplating 1526.1.1 Hood Design 1526.1.2 Airflow 1556.2 Spray Painting 1596.2.1 Hood Design 1596.2.2 Airflow 1636.3 Processing and Transfer of Granular Material 1656.4 Welding, Soldering, and Brazing 1696.5 Chemical Processing 1776.5.1 Chemical Processing Operations 1786.6 Semiconductor Gas Cabinets 1876.6.1 Entry Loss 1906.6.2 Optimum Exhaust Rate 1916.7 Low-Volume  High-Velocity Systems for Portable Tools  192Example 6.1 Calculation of Exhaust Rate for Open-Surface Tanks 199Example 6.2 Design of a Low-Volume  High-Velocity Exhaust System  200List of Symbols 201References 2027 Chemical Laboratory Ventilation 2047.1 Design of Chemical Laboratory Hoods 2057.1.1 Vertical Sliding Sash Hoods 2057.1.2 Horizontal Sliding Sash Hoods 2097.1.3 Auxiliary Air Supply Hoods 2127.2 Face Velocity for Laboratory Hoods 2147.3 Special Laboratory Hoods 2167.4 Laboratory Exhaust System Features 2177.4.1 System Configuration 2177.4.2 Construction 2187.5 Factors Influencing Hood Performance 2207.5.1 Layout of Laboratory 2207.5.2 Work Practices 2227.6 Energy Conservation 2247.6.1 Reduce Operating Time 2247.6.2 Limit Airflow 2257.6.3 Design for Diversity 2277.6.4 Heat Recovery 2277.6.5 Ductless Laboratory Hoods 2277.7 Performance of Laboratory Hoods 2287.8 General Laboratory Ventilation 229References 229Problems 2308 Design of Single-Hood Systems 2328.1 Design Approach 2338.2 Design of a Simple One-Hood System (Banbury Mixer Hood) 2348.3 Design of a Slot Hood System for a Degreasing Tank 2418.3.1 Loss Elements in a Complex Hood 2418.3.2 Degreaser Hood Design Using Velocity Pressure Calculation Sheet (Example 8.2) 2458.4 Pressure Plot for Single-Hood System 247List of Symbols 247Example 8.1 Banbury Mixer System Designed by the Velocity Pressure Method 248Example 8.2 Degreaser System Designed by the Velocity Pressure Method 250References 251Appendix: Metric Version of Example 8.1 252Problems 2529 Design of Multiple-Hood Systems 2549.1 Applications of Multiple-Hood Systems 2549.2 Balanced Design Approach 2569.3 Static Pressure Balance Method 2609.3.1 Foundry Cleaning Room System (Example 9.1) 2609.3.2 Electroplating Shop (Example 9.2) 2629.4 Blast Gate Balance Method 2659.5 Other Computational Methods 265List of Symbols 266Example 9.1 Foundry Cleaning Room Designed by Static Pressure Balance Method 267Example 9.2 Electroplating Shop System Designed by Static Pressure Balance Method 272References 278Additional Reading 279Appendix: Metric Version of Example 9.1 28010 Fans and Blowers 28210.1 Types of Air Movers 28310.1.1 Axial Flow Fans 28310.1.2 Centrifugal Fans 28510.1.3 Air Ejectors 28710.2 Fan Curves 28810.2.1 Static Pressure Curve 28910.2.2 Power Curve 29110.2.3 Mechanical Efficiency Curve 29310.2.4 Fan Laws  29510.2.5 Relationship between Fan Curves and Fan Tables 29710.3 Using Fans in Ventilation Systems 29810.3.1 General Exhaust Ventilation Systems 29810.3.2 Local Exhaust Ventilation Systems 30010.4 Fan Selection Procedure 305List of Symbols 308References 309Problems 30911 Air-Cleaning Devices 31111.1 Categories of Air-Cleaning Devices 31211.1.1 Particle Removers 31211.1.2 Gas and Vapor Removers 32211.2 Matching the Air-Cleaning Device to the Contaminant 32511.2.1 Introduction 32511.2.2 Device Selection 32611.3 Integrating the Air Cleaner and the Ventilation System 32611.3.1 Gravity Settling Devices 33011.3.2 Centrifugal Collectors 33011.3.3 Filters 33111.3.4 Electrostatic Precipitators 33411.3.5 Scrubbers 33411.3.6 Gas and Vapor Removers 335List of Symbols 336References 337Problems 33712 Replacement-Air Systems 33812.1 Types of Replacement-Air Units 34012.2 Need for Replacement Air 34112.3 Quantity of Replacement Air 34212.4 Delivery of Replacement Air 34412.4.1 Replacement-Air System 1 (RAS-1), Melting Furnaces 34912.4.2 Replacement-Air System 2 (RAS-2), Floor Casting 34912.4.3 Replacement-Air System 3 (RAS-3), Sand Handling 35012.4.4 Replacement-Air System 4 (RAS-4), Shakeout 35112.5 Replacement Air for Heating 35212.6 Energy Conservation and Replacement Air 35312.7 Summary 356References 35613 Quantification of Hood Performance 35813.1 Hood Airflow Measurements 35913.2 Hood Capture Efficiency 36013.2.1 Influence of Cross-Drafts on Hood Performance 36113.2.2 Relationship between Airflow Patterns and Capture Efficiency 36313.2.3 Shortcomings of the Centerline Velocity Approach 37013.3 Use of Capture Efficiency in Hood Design 372List of Symbols 372References 37314 Application of Computational Fluid Dynamics to Ventilation System Design 37414.1 Introduction 37414.2 Methods 37614.2.1 Grid-Based Methods 37714.2.2 Grid-Free Methods 37814.3 Applications 37914.3.1 Historical Perspectives 37914.3.2 Current Progress 38014.4 Issues on the Use of Computational Fluid Dynamics 38614.5 Commercial Codes: Public-Domain Information 387References 387Appendix 38915 Reentry 39115.1 Airflow around Buildings 39315.2 Measurement of Reentry 39615.3 Calculation of Exhaust Dilution 40115.4 Scale Model Measurement 40415.5 Design to Prevent Reentry 40615.5.1 Stack Height Determination 40715.5.2 Good Engineering Practices for Stack Design 408List of Symbols 412References 413Problems 415Index 417

"…clearly a definitive first class publication on industrial ventilation…if your goal is to expand your knowledge of ventilation this a great place to start." (Chemical Health and Safety, January-February 2005)