“…Organic monomeric amines such as tetraethylenepentamine, N , N ′-bis(2-hydroxyethyl)ethylenediamine, tetrakis(hydroxyethyi)ethylenediamine, and polymeric imines such as poly(propylenimine), polyethylenimine, − polystyrene-bound ethylene diamine, aminoalkyl poly(dimethylsiloxane), , alkylamine functionalized polysiloxanes, − and so forth containing primary, secondary, or tertiary amine groups are known to be somewhat sensitive to CO 2 gas . The hard acid CO 2 can efficiently bind with hard base amino groups to form carbamates or bicarbonates (in the presence of humidity) and as a consequence of which the response in terms of resistance or impedance increases.…”