Prehospital acute blunt thoracic trauma care remains difficult. Among then, diagnosis of atelectasis with ultrasound remains rare and unusual. We report the case of a worker who had a sharp chest pain currently after using a jackhammer. First clinical examination suspected a left tension pneumothorax but ruled out by sliding sign in left hemithorax ultrasound (US) examination. The right upper thoracic scan showed a well-defined lung point, a "hepatization" appearance with static air bronchograms, a diaphragm elevation and a dextrocardia in B mode, and a pseudobarcode with no lung pulse in Time Motion (TM) mode. A "rip's organ absent sign" excluded the hypothesis of an acute diaphragmatic rupture. An atelectasis was at once suspected and confirmed at hospital by tomodensitometry. Diaphragmatic injury can be suspected when "rip's absent organ sign," diaphragm poor movement or elevation, liver sliding sign, subphrenic effusion, or spleen or liver intrathoracic presence. Unusually, these signs can put diagnosis in a wrong track as described in our case report. Lung pulse, absent sliding sign, or hemidiaphragm standstill is highly suspect of atelectasis but cannot be established formally. However, in patients with alveolar consolidation displaying air bronchograms, the dynamic air bronchograms indicated lung contusion, distinguishing it from atelectasis. Static air bronchograms were seen in most atelectases and one-third of cases of contusion or pneumonia. Fast scan can be useful to evoke atelectasis in blunt trauma. Differential diagnoses such as diaphragmatic rupture or consolidation could be discarded. Ultrasound examination could justify a precise semiological description.