Mass release rate Q

kg/s

Stack / release height H

Wind speed u

m/s

Stability class

Terrain

Receiver distance x

Ambient temperature

°C

Ambient pressure

kPa

Pasquill-Gifford derivation, Briggs σ coefficients, stability class selection, and limitations.

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Centerline ground-level concentration:

C = Q / (π · u · σ_y · σ_z) · exp(−H² / (2 σ_z²))

ppm conversion:

ppm = C (kg/m³) · 10⁶ · R · T / (P · MW_H₂S)

Thresholds: ERPG-2 = 30 ppm · ERPG-3 / IDLH = 100 ppm

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