1. Rapidly deteriorating or likely to require escalation to high flow oxygen, invasive or non-invasive ventilatory support within 24 hours according to Investigator’s opinion. 2. Unable to safely receive a nebulized treatment for approximately 4 minutes according to Investigator’s opinion. 3. Unable to receive or considered ineligible for invasive or non-invasive ventilatory support. 4. History of methemoglobinemia. 5. Uncontrolled asthma or history of severe bronchospasm. 6. Severe (requiring baseline oxygen therapy > 12 h/day prehospitalization) chronic respiratory disease (e.g., known COPD, pulmonary arterial hypertension, idiopathic pulmonary fibrosis, interstitial lung disease). 7. Suspected or confirmed untreated, active tuberculosis. 8. Severely immune-compromised participants in Investigator’s opinion. 9. Recent (within 3 months) active coronary artery disease or decompensated heart failure (New York Heart Association class 3-4). 10. Presence of tracheostomy. 11. Chronic (≥4 weeks) use of corticosteroids >10 mg/day of prednisone or equivalent within 4 weeks of randomization. 12. Participation in other clinical investigations utilizing investigational treatment or within 30 days / 5 half-lives whichever is longer. 13. Clinically significant abnormalities in clinical chemistry or hematology at screening, defined as: Platelet count <50,000 mm3. Alanine aminotransferase or aspartate aminotransferase >5 × upper limit of normal (ULN). Estimated glomerular filtration rate <30 mL/min/1.73 m2(modification of diet in renal disease formula) or requiring hemofiltration or dialysis. 14. Anticipated transfer to another hospital which is not a study site during the treatment period. 15. Allergy to any of the components of the study intervention.

1. Rapidly deteriorating or likely to require escalation to high flow oxygen, invasive or non-invasive ventilatory support within 24 hours according to Investigator’s opinion. 2. Unable to safely receive a nebulized treatment for approximately 4 minutes according to Investigator’s opinion. 3. Unable to receive or considered ineligible for invasive or non-invasive ventilatory support. 4. History of methemoglobinemia. 5. Uncontrolled asthma or history of severe bronchospasm. 6. Severe (requiring baseline oxygen therapy > 12 h/day prehospitalization) chronic respiratory disease (e.g., known COPD, pulmonary arterial hypertension, idiopathic pulmonary fibrosis, interstitial lung disease). 7. Suspected or confirmed untreated, active tuberculosis. 8. Severely immune-compromised participants in Investigator’s opinion. 9. Recent (within 3 months) active coronary artery disease or decompensated heart failure (New York Heart Association class 3-4). 10. Presence of tracheostomy. 11. Chronic (≥4 weeks) use of corticosteroids >10 mg/day of prednisone or equivalent within 4 weeks of randomization. 12. Participation in other clinical investigations utilizing investigational treatment or within 30 days / 5 half-lives whichever is longer. 13. Clinically significant abnormalities in clinical chemistry or hematology at screening, defined as: Platelet count <50,000 mm3. Alanine aminotransferase or aspartate aminotransferase >5 × upper limit of normal (ULN). Estimated glomerular filtration rate <30 mL/min/1.73 m2(modification of diet in renal disease formula) or requiring hemofiltration or dialysis. 14. Anticipated transfer to another hospital which is not a study site during the treatment period. 15. Allergy to any of the components of the study intervention.