To assess if a ventilation unit to be installed in industrial painting boxes is in the scope of Regulation (EU)1253/2014, first of all the general guidance principle laid down in the above question and answer should be considered (product functionality and presence of human beings). Moreover, concerning the specific questions:
if a ventilation unit is to be installed in an industrial painting box that operates with both a potentially explosive atmosphere (under the sense of the ATEX Directive), as it is normally the case of solvent-based paintings, and a non-explosive atmosphere, as it is normally the case of water-based paintings, such ventilation unit is in scope of Regulation (EU)1253/2014 (as the scope exclusion under its article 1.2.d is about ventilation units which are exclusively specified as operating in a potentially explosive atmosphere);
a painting box with water-based paint cannot be interpreted as an abrasive environment unless clear evidence is provided that this environment causes accelerated wear on the fan / impeller blades of the ventilation unit.
Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.