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

**URL:** <https://forums.buildingsmart.org/t/data-type-for-storing-concentration-e-g-ppm-for-co2/4022>\
**Category:** IFC\
**Created:** [December 8, 2021, 7:34pm UTC](https://forums.buildingsmart.org/t/data-type-for-storing-concentration-e-g-ppm-for-co2/4022 "2021-12-08T19:34:42Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![ElisEck](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.buildingsmart.org/eliseck/32/1521_2.png) [@ElisEck](https://forums.buildingsmart.org/u/ElisEck)\
**Post date:** [December 8, 2021, 7:34pm UTC](https://forums.buildingsmart.org/t/data-type-for-storing-concentration-e-g-ppm-for-co2/4022/1 "2021-12-08T19:34:42Z")

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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?

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**Author:** ![aothms](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@aothms](https://forums.buildingsmart.org/u/aothms)\
**Post date:** [December 11, 2021, 1:15pm UTC](https://forums.buildingsmart.org/t/data-type-for-storing-concentration-e-g-ppm-for-co2/4022/2 "2021-12-11T13:15:33Z")

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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](https://github.com/buildingSMART/IFC4.3.x-development/issues/71)

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.

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**Author:** ![BFerries](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.buildingsmart.org/bferries/32/1377_2.png) [@BFerries](https://forums.buildingsmart.org/u/BFerries)\
**Post date:** [December 16, 2021, 3:24pm UTC](https://forums.buildingsmart.org/t/data-type-for-storing-concentration-e-g-ppm-for-co2/4022/3 "2021-12-16T15:24:46Z")

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Two psets are dedicated to environmental impacts:

- [Pset\_EnvironmentalImpactIndicators](https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/link/pset_environmentalimpactindicators.htm)
- [Pset\_EnvironmentalImpactValues](https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/link/pset_environmentalimpactvalues.htm)

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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**Author:** ![ElisEck](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.buildingsmart.org/eliseck/32/1521_2.png) [@ElisEck](https://forums.buildingsmart.org/u/ElisEck)\
**Post date:** [January 21, 2022, 6:14pm UTC](https://forums.buildingsmart.org/t/data-type-for-storing-concentration-e-g-ppm-for-co2/4022/4 "2022-01-21T18:14:18Z")

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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…