Natural ventilation on a hangar

Interesting question. The intent of the credit is to prevent pollutants from entering occupied spaces. If we consider the hangar to be a garage, then the hangar is the space with contaminants from which other spaces need to be protected. Therefore I would say the credit could apply if you can meet the separation and negative pressure requirements with the natural ventilation, and there are other occupied spaces in the building, i.e. a small office. If it just a big open hangar, then it probably doesn't meet the intent of the credit.