Position-Aware Coupling Between Ozone and Welding Fume Peaks Under Local Exhaust Ventilation

Real-time management of short-term ozone peaks during arc welding remains challenging because ventilation- and enclosure-defined transport boundaries can create strong position-dependent peak behavior, even under fixed process settings. This study establishes a coordinate-referenced, event-level monitoring and analysis framework to quantify ozone–fume peak coupling under a controlled local exhaust ventilation (LEV) suction boundary during CO₂ arc welding. A controlled process–environment testbed with a defined suction condition was implemented, and synchronized ozone and fume signals were acquired at three sampling points referenced to the arc position and the LEV inlet direction. The particulate channel was anchored to a PM₄ gravimetric reference, yielding a condition-specific traceable CPM-to-mass conversion factor K₁ of 1.76 × 10⁻² mg/(m³·CPM) and enabling standardized peak-fume endpoints on a mass-concentration scale. The primary inferential analysis used the curtain-on dataset, comprising 21 sessions and 42 event-level records balanced across three sampling points. Under the same suction boundary, peak coupling was strongly monitoring-coordinate dependent: LEV-aligned locations showed statistically supported ln–ln scaling between peak ozone and peak fume, whereas the opposite-side location did not exhibit statistically supported scaling; a pooled point-parameterized ln–ln model achieved an adjusted R² of 0.777. As a descriptive control-relevant contrast, adding a curtain enclosure under continuous LEV produced strong event-level ozone peak suppression at LEV-aligned locations, with a maximum reduction of 87.8%, while attenuation at the opposite-side location remained limited. Overall, the results provide a ventilation-boundary-consistent, coordinate-specific basis for monitoring placement and control evaluation, identifying where peak translation is supported and where direct ozone monitoring remains necessary.