Data Type for storing concentration e.g. ppm for CO2

Neither in IfcMeasureValue nor in IfcDerivedMeasureValue I can find an appropriate choice for storing CO2 concentration which is usually given in ppm. Is using IfcInteger really the best available option? Or is the use of IfcPositiveRatioMeasure intended?

We had a discussion here on unitless / identity units Proposal to split UnitBasis attribute for IfcCostValue into UnitBasis and UnitValue · Issue #71 · buildingSMART/IFC4.3.x-development · GitHub

The tentative conclusion was to add a COUNTUNIT to IfcUnitEnum, that way you can probably model your ppm as a derived unit of 1e1 COUNT / 1e6 COUNT (but that last part I didn’t work out in detail).

Feel free to chime into the discussion there.

Two psets are dedicated to environmental impacts:

The rigth indicator for CO2 concentration is “climate change” as an IfcMassMeasure because it is the “Quantity of greenhouse gases emitted calculated in equivalent CO2”.

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That was actually not what I was intending to do. I am dealing with indoor air quality which is usually given in ppm, CO2 emissions are a different thing…