Models for nearly every occasion: Part IV - Two-box decreasing emission models.

Area of Science:

• Occupational Health and Safety
• Environmental Engineering
• Industrial Hygiene

Background:

• Traditional models often lack specificity for localized control strategies.
• Assessing airborne contaminant concentrations with local exhaust ventilation (LEV) and filtered recirculation requires advanced modeling.
• Understanding contaminant dynamics in well-mixed rooms with complex ventilation is crucial for worker safety.

Purpose of the Study:

• Introduce novel two-box "well-mixed room" decreasing emission (DE) models.
• Provide models for scenarios with local controls, including local exhaust and filtered return air.
• Develop both steady-state and transient near- and far-field models for various control device scenarios.

Main Methods:

• Presentation of steady-state and transient near- and far-field models for each control device.
• Utilizing transient equations to predict concentration over time (t) post-substance application.
• Employing steady-state equations for predicting average concentration per application and time-weighted average (TWA) exposures under specific conditions.
• Proposing a structured calibration procedure based on a mass balance approach for each model.

Main Results:

• Models predict concentrations for steady-state and transient conditions, applicable to continuous or intermittent substance applications.
• Steady-state equations facilitate TWA calculation when initial/final concentrations are near zero.
• Transient equations are essential for predicting TWA exposures when steady-state criteria are unmet, or for short-term/peak exposures.
• Calibration procedures enable estimation of applied mass, near-field flowrate, and system efficiencies (e.g., capture and filtration).

Conclusions:

• The new DE models offer a robust framework for assessing airborne contaminants in rooms with local controls.
• Models provide flexibility for predicting both long-term average and short-term peak exposures.
• Calibration methods ensure accurate parameter estimation for practical application in industrial hygiene and safety assessments.