Hi John,
our institute has developed a gas sensor, which enables measurement
of high doses of carbon dioxide in dry air. You can see it's principle
if you follow our homepage http://141.30.124.127.
Is is not commercially available. However, our partner company (Aktiv
Sensor, Ruhlsdorfer Str. 95, Gebaeude 5A, 14532 Stahnsdorf, Germany)
thinks about production of prototypes in the next time.
Best regards
Reinhard