Here, we
investigated the pressure response of five different models of portable
CO₂ infrared sensors: GMP343 (Vaisala Oyj, Finland), ADC LCA-2 (The
ADC Bioscientific Ltd., UK), and three different EGMs (PP Systems, UK). In the
pressure range of 750–1000 hPa, we found that the analysers function
systematically in an individual manner and the original pressure corrections
that the manufacturers have provided are inaccurate from a few to tens of ppm.
Therefore, we determined new empirical pressure correction functions for each
sensor. The resulting corrections perform better than the original ones in the
pressure, CO₂ concentration (370–490 ppm), temperature (5–21 deg.C)
and water-vapour (4–11 g m^–3) range of this study. However, since the
individual analysers had different pressure responses, we recommend that each
individual instrument be tested in cases where changes in pressure may affect
the results.