Haldane's carbonic acid (carbon dioxide) apparatus

This was invented by Haldane in 1902 for use in connection with a Government enquiry into the ventiliation of factories and workshops. By its means an accurate analysis of the amount of carbon dioxide in the air could be performed in a few minutes. Pure dry air contains carbon dioxide in the average proportion of 3 volumes to 10,000. Air containing more than 10 volumes of carbon dioxide becomes oppressive to breathe, but during the enquiry as much as 38 volumes per 10,000 were sometimes found.