Checks (measured vs predicted)
The science
Steady continuous release in a uniform wind u follows the Gaussian plume C(x,y,z) = Q/(2π u σy σz) · exp(−y²/2σy²) · [exp(−(z−H)²/2σz²) + exp(−(z+H)²/2σz²)], the second term being the reflection from the ground. The spreads σy(x), σz(x) are the Briggs rural correlations for Pasquill classes A (very unstable) to F (stable). Concentration in ppm uses methane M = 16.04 g/mol and 40.9 mol/m³ of air at 25 °C. A ground-level source gives C = Q/(π u σy σz) on the axis, and the flux integral of C u over any downwind plane returns Q.
Simplifications: steady wind, flat terrain, no chemical loss, valid beyond about 100 m, no plume rise or buoyancy. Sensors read time-averaged concentrations at 1.5 m. Educational model, not a safety tool.