Dust Doctor: Ways to control airborne contaminants in your plant
In a bulk solids plant, a dust control system minimizes worker exposure to nuisance and hazardous materials by controlling dust. The two ventilation methods most commonly used in dust control systems are dilution ventilation and local exhaust ventilation. One reason that a dilution ventilation system appeals to many users is that they can apply it without knowing very much about dust control practices. Using a local exhaust ventilation system, on the other hand, requires a detailed knowledge of the user's bulk solids process and dust control equipment, including dust capture hoods, ducts, exhaust fans, and dust collectors. However, this system requires far less makeup air than dilution ventilation.
How dilution ventilation works
Dilution ventilation controls dust by diluting the contaminant concentration with clean air after the contaminant passes through the worker's breathing zone. The method circulates and mixes the air through the workplace, changing all the workplace air over a period of up to many hours. Because it evenly exhausts a relatively large volume of air from the workplace, the method requires a large volume of makeup air. A variation of this method adapted from cleanroom applications, known as displacement ventilation, typically uses a downward laminar [that is, nonturbulent] flow of clean air to protect the process powder from workers and other contamination sources.