To set the zero on the IRGA, it is necessary to provide it with a source of CO2-free air. This is accomplished by pumping air through a column containing soda lime, which removes CO2. A small amount of glass wool should be placed towards the outlet of the column, and the column should then be filled with soda lime using a spatula. When the column is full, it should be tapped on the desk to settle the soda lime, and then topped off. The end cap should then be inserted in the column, and used to compress the soda lime so that the column is tightly packed. The column should then be mounted VERTICALLY on the laboratory stand.

The soda lime has a coloured indicator to show when it is spent. The soda lime should be replaced when most of it has changed from its original white colour to a pale purple. This colour change is subtle, and the purple coloration often does not persist, but appears as a band in the column at the junction between active and inactive soda lime.

Producing Area:Canada