- patients requiring invasive (mechanical ventilation) or non-invasive (cpap, bipap for hypoxemia) ventilation or ecmo (note: oxygen supplementation using high flow oxygen systems or low flow oxygen systems would not exclude patients from this study) - intractable metabolic acidosis - cardiogenic pulmonary edema - hypotension requiring use of vasopressors - hyperferritinemia (serum ferritin ≥2,000 mcg/l) - white blood cell count > 50,000/mm3 - participation in another interventional clinical trial for covid-19 therapy - highly immunosuppressive therapy or anti-cancer combination chemotherapy within 24 hours prior to first dose of sargramostim - known or suspected intolerance or hypersensitivity to sargramostim, or any component of the product - previous experience of severe and unexplained side effects during aerosol delivery of any kind of medical product - presence of any preexisting illness that, in the opinion of the investigator, would place the patient at an unreasonably increased risk through participation in this study - pregnant or breastfeeding females - severe or uncontrolled pulmonary comorbid conditions, including systemic steroid dependent asthma, systemic steroid dependent copd, oxygen dependent copd, lung transplant, known interstitial lung disease, or cystic fibrosis

- patients requiring invasive (mechanical ventilation) or non-invasive (cpap, bipap for hypoxemia) ventilation or ecmo (note: oxygen supplementation using high flow oxygen systems or low flow oxygen systems would not exclude patients from this study) - intractable metabolic acidosis - cardiogenic pulmonary edema - hypotension requiring use of vasopressors - hyperferritinemia (serum ferritin ≥2,000 mcg/l) - white blood cell count > 50,000/mm3 - participation in another interventional clinical trial for covid-19 therapy - highly immunosuppressive therapy or anti-cancer combination chemotherapy within 24 hours prior to first dose of sargramostim - known or suspected intolerance or hypersensitivity to sargramostim, or any component of the product - previous experience of severe and unexplained side effects during aerosol delivery of any kind of medical product - presence of any preexisting illness that, in the opinion of the investigator, would place the patient at an unreasonably increased risk through participation in this study - pregnant or breastfeeding females - severe or uncontrolled pulmonary comorbid conditions, including systemic steroid dependent asthma, systemic steroid dependent copd, oxygen dependent copd, lung transplant, known interstitial lung disease, or cystic fibrosis

- intubated and supported by mechanical ventilation - intractable metabolic acidosis - cardiogenic pulmonary edema - hypotension requiring use of vasopressors - hyperferritinemia (serum ferritin ≥2,000 mcg/l) - white blood cell count > 50,000/mm3 - participation in another interventional clinical trial for covid-19 therapy - highly immunosuppressive therapy or anti-cancer combination chemotherapy within 24 hours prior to first dose of sargramostim - known or suspected intolerance or hypersensitivity to sargramostim, or any component of the product - previous experience of severe and unexplained side effects during aerosol delivery of any kind of medical product - presence of any preexisting illness that, in the opinion of the investigator, would place the patient at an unreasonably increased risk through participation in this study - pregnant or breastfeeding females

- intubated and supported by mechanical ventilation - intractable metabolic acidosis - cardiogenic pulmonary edema - hypotension requiring use of vasopressors - hyperferritinemia (serum ferritin ≥2,000 mcg/l) - white blood cell count > 50,000/mm3 - participation in another interventional clinical trial for covid-19 therapy - highly immunosuppressive therapy or anti-cancer combination chemotherapy within 24 hours prior to first dose of sargramostim - known or suspected intolerance or hypersensitivity to sargramostim, or any component of the product - previous experience of severe and unexplained side effects during aerosol delivery of any kind of medical product - presence of any preexisting illness that, in the opinion of the investigator, would place the patient at an unreasonably increased risk through participation in this study - pregnant or breastfeeding females