Since its first edition in 1951, "Industrial Ventilation: A Manual of Recommended Practice for Design" has been used by engineers, regulators and industrial hygienists to design and evaluate industrial ventilation systems. Beginning with the 26th edition, the "Manual" has undergone several major reorganizations and upgrades--the addition of a second compendium "Manual" dedicated to operation and maintenance; subsequent additions of chapters on organization and evaluation of systems; metric solutions and tables; and calculation sheets and methods. Now in its 30th edition, changes in many of the chapters and conceptual figures that incorporate computational fluid dynamics (CFD) have been added for clarification and incorporated for simpler conceptual understanding of airflow patterns. Care has been taken to make this "Manual" a practical user's handbook, written with deference toward a simpler and more concise means of explanation. In addition, the "Manual" incorporates a new control concept for vacuum extraction on welding guns to complement the four new conceptual design strategies found in the 29th edition.