What assessments would allow you to best differentiate a pneumothorax from a hemothorax?

CXR: Pneumothorax is air in the pleural cavity and corresponding partial or full collapse of the lung. Hemothorax is blood in the pleural cavity with compression of the lung. Hemothorax occurs most often in the setting of trauma. Pneumothorax can also occur from trauma, but also spontaneously if there is a lung "bleb". Both can occur simultaneously. Cxr is usually the tool, occasionally chest ct/us.

Simple: Simple chest x-ray pa and lateral views or cat scan thorax diagnostic.