Atmospheric Pressure Peak Area Correction for Gas Chromatography with Standard Detectors // Corrects gas-chromatography peak areas for the influence of ambient air pressure on standard detectors open to the ambient atmosphere, such as the flame ionization detector, whose pressure sensitivity was characterised by Bocek, Novak and Janak (1969) doi:10.1016/S0021-9673(00)99223-9. Unlike the pressure compensation of Ayers and Clardy (1985) https://patents.google.com/patent/US4512181A, which is combined with a calibration and valid only for a single calibration period of a few days, per-cylinder peak areas are decomposed by principal components into a pressure-correlated component and per-peak drift; a common pressure-sensitivity coefficient (kappa) is estimated with a heavy-tail-robust fit on a drift- reduced signal, and slow drift plus a daily factor are removed. Returns the corrected areas together with a chi-square goodness-of-fit diagnostic. Structural-break detection (package 'strucchange', Zeileis and others (2002) doi:10.18637/jss.v007.i02) is provided for episode-level and variance breakpoint analysis.