When writing a topic which includes units of measurement, you are advised to insert a non-breaking space between the value and unit. As a result, the two elements will not be separated at the end of a line. You can create a shortcut to insert a non-breaking space as follows:

1. Choose Options > Preferences > Document Type Association.
2. Click DITA from the list on the right-hand side so that it is highlighted and click the Edit button.
3. In the Document type window, click the Author tab, select Actions and then click the plus button at the bottom.
4. In the Action window, fill in the ID, description and name for the new action.
   An ID is required, but a name and description might be useful to look up the action. For example, a meaningful name could be non-breaking space.
5. In the Shortcut key box, enter the shortcut you want to use for a non-breaking space.
   For example, Ctrl+Shift+Space.
6. In the Activation XPath box, type true().
7. Click the Choose button in the Operation box, select InsertFragmentOperation from the Class list and click OK.
8. Double-click the new action labeled fragment and type in the Value box.
9. Click OK to save and close the windows.

You will now be able to use the shortcut key to insert a non-breaking space in oXygen.