The Art and Science of Industrial Ventilation
By Ed Rutkowski
Approximately thirty years ago, not long after George Gruetzmacher got his start in industrial hygiene, tuberculosis was a major concern for OEHS professionals whose practice concerned industrial ventilation. In recent years, of course, control of a different disease—COVID-19—has been the major focus of many ventilation applications. Last week at AIHce EXP 2023, Gruetzmacher delivered a presentation informed by the applications of industrial ventilation to the two diseases that bookend his career and the many other hazards for which ventilation is a preferred means of protecting worker health.
Gruetzmacher has spent 35 years working for the OSHA on-site consultation program in Wisconsin. In this role, he has visited employers, performed IH exposure assessments, and helped businesses control health hazards. His presentation—which, he was quick to point out, reflected his own opinions and not those of his employer—attempted to bridge gaps in understanding between the manufacturers of ventilation systems and OEHS professionals.
OEHS professionals’ goal, Gruetzmacher said, is to keep workplace exposures to contaminants—which are typically measured in micrograms per cubic meter, or mg/m3—below an occupational exposure limit 95 percent of the time. Such a goal is difficult to explain to ventilation manufacturers, whose main metric is cubic feet per minute, or cfm. “That is the fundamental issue,” Gruetzmacher said. “We ask someone selling us something to deliver, but we’re talking different languages.”
Gruetzmacher next provided basic explanations of the three main types of industrial ventilation: dilution ventilation, which mixes potentially contaminated air with fresh air; displacement ventilation, which replaces contaminated air with fresh air; and local exhaust, which pulls contaminants from their source. These systems tend to have many of the same components: a fan, ductwork, filters. A key decision when designing and implementing a ventilation system concerns whether to recirculate the air or exhaust it outdoors.
Perhaps the most important part of the system is the hood, which is where the contaminants enter the ductwork. Gruetzmacher suggested that designing an effective hood requires effective communication between the manufacturer and the OEHS professional. A ventilation engineer who is designing a spray booth, for example, will likely not consider how the presence of a worker affects the movement of air. OEHS professionals need to provide that perspective because, as Gruetzmacher said, “we can’t spend half a million dollars to build a model of every workstation.”
Gruetzmacher closed his presentation by sharing a list of essential resources, including the ACGIH publications Industrial Ventilation: A Manual of Recommended Practice for Design and Industrial Ventilation: A Manual of Recommended Practice for Operation and Maintenance; the ASHRAE Handbook—HVAC Applications; and the ANSI/ASSP standard Z9.2-2018, Fundamentals Governing the Design and Operation of Local Exhaust Ventilation (LEV) Systems. “If [a manufacturer has] nothing on this list, I would be very suspicious about their ability to design, fabricate, install, and operate your ventilation system,” Gruetzmacher said.
Ed Rutkowski is editor in chief of The Synergist.
For Further Reading
The Synergist: “Approaches to Ventilation Systems: A Survey of ANSI Z9 Standards” (February 2023).
The Synergist: “Bridging the Gaps: IHs Can Connect Ventilation Engineering, IAQ, and Infection Control” (April 2023).
The Synergist: “Troubleshooting Industrial Ventilation: Simple Tools for Finding Problems in LEV Systems” (June/July 2016).
The Synergist: “Ventilation and Sustainable Laboratories: How Industrial Hygienists Can Influence Laboratories’ Effects on Environment and Climate” (February 2022).