Openbox checks all units in the model, so it can warn you about formulas which make no sense because they combine inputs in a way that “adds apples and oranges”. For example, there might be two calculations in the model, one in Euros and one in US dollars. These should not be combined without applying an exchange rate.

Units are calculated for each formula, based on the calculations that feed into it. For example, if a calculation takes a number in Euros, and divides it by a number in tonnes, the result must have units of “Euros per tonne”. Openbox will warn you if this is not the case by highlighting the units in red.

The first thing to do if the units are shown in red is to check that the calculation does make sense. For instance, have you applied all necessary conversion factors and exchange rates?

You have three options for fixing units in red:

• Correct the units, if you decide they are wrong
• Tell Openbox to try and correct them itself by clicking the units text, then clicking “Use expected”
• Tell Openbox to stop flagging this unit as wrong. Click the units text and then tick the “Ignore issues” box, then click “OK”.

You can also simply ignore the red text. It will not stop the model being built, but it should be treated as a warning, so we do not recommend this approach.