Benefits of Designing for Ventilation Diversity in a Large Industrial Research Laboratory—A Case Study

Abstract

Abstract This article illustrates both initial installation and ongoing operational benefits of designs that take advantage of the statistical diversity of laboratory safety hood active use. Hoods are typically in active use, with their sashes open, less than 15 percent of the time. The collective behavior of a group of variable air flow hoods is readily modeled as a stochastic process. Hoods designed for nearly constant face velocity, so that their exhaust flow is reduced when they are closed and increased when they are in active use, yield large economic benefits. The average exhaust flow from a group of hoods is shown to be a small fraction of the maximum flow required when all hoods are simultaneously open. More importantly, the maximum probable flow is a small fraction of the maximum flow because there is a vanishingly small probability that all hoods will be simultaneously in active use. This article offers a complete design analysis for a large laboratory and discusses the design trade-offs that, taken together, can produce economic operation while enhancing safety and health.