Background: Hypersensitivity pneumonitis, also known as extrinsic allergic alveolitis, is a pulmonary disease with large knowledge gaps, including etiology, pathogenesis, diagnosis, and treatment. Case Report: A 58-year-old male with a pertinent history of recurrent Mycobacterium malmoense presented to a tertiary emergency department after 1 week of difficulty breathing. He also reported a productive cough and fevers. The patient was an active smoker and was recently exposed to chemical fire-retardant spray. Chest x-ray showed extensive bilateral pulmonary infiltrates. The tertiary center initiated cefpodoxime 200 mg twice daily for 5 days and home azithromycin for possible pneumonia. However, the patient returned the next day with worsening symptoms. After the patient transferred to our institution, physical examination revealed a hypoxic patient with bibasilar crackles and wheezes. Laboratory tests revealed elevated white blood cell count, sedimentation rate, and immunoglobulin E. Chest computed tomography demonstrated growth of a previously noted right upper lobe intracavitary lesion and new onset diffuse interstitial pulmonary ground-glass airspace opacities. Hypersensitivity pneumonitis panel demonstrated positive antibodies to Aspergillus fumigatus antibody precipitin 1 and Micropolyspora faeni. The patient was given oral prednisone and advice on proper respiratory precautions in the workplace. Conclusion: This case illustrates that hypersensitivity pneumonitis can develop via chemical fire-retardant spray. Additionally, patients with a smoking history and elevated immunoglobulin E should be evaluated for severe forms of the disease.