A Phase 2 Study to Determine the Safety and Efficacy of AIR001 in Subjects With Pulmonary Arterial Hypertension (PAH)

Inclusion Criteria: 1. Signed and dated informed consent document 2. Able to comply with study procedures 3. Diagnosis of PAH as classified by: 1. Idiopathic (IPAH) or heritable(HPAH); or 2. PAH associated with CTD; Systemic Sclerosis, Limited Scleroderma, Mixed, SLE, or overlap syndrome; 3. PAH associated with HIV ii. Simple, congenital shunts at least one year post repair. iii. Exposure to legal drugs, chemicals and toxins 4. Cardiac catheterization prior to Screening with: 1. mPAP ≥ 25 mmHg (at rest); 2. PCWP ≤ 15 mmHg; and 3. PVR \> 3 mmHg/L/min or 240 dyn.sec/cm5 5. A qualification cardiac catheterization, to confirm the persistence and severity of PAH, if the diagnostic catheterization was performed more than 30 days prior to Baseline 1. Confirms diagnosis; 2. PVR above 300 dyn.sec/cm5 to demonstrate the persistence and severity of PAH; and 3. No change in disease-specific PAH therapy since the qualification catheterization used 6. Newly diagnosed PAH on no disease-specific PAH therapy or previously diagnosed on oral disease-specific PAH therapy for 90 days prior with either an ETRA and/or PDE-5i 7. Has PFTs within 180 days prior to Baseline with no evidence of significant parenchymal lung disease defined as: * FEV1 ≤ 70% (predicted) (pre-bronchodilators); * FEV1/FVC ≤ 70% (pre-bronchodilators); or * Total lung capacity \< 70% (predicted). 8. Has WHO/NYHA FC II- IV. 9. ≥ 18 and ≤ 75 years. 10. Weight ≥ 40 kg. 11. Has 6MWT distance at least 50 meters. 12. Had a V/Q scan or pulmonary angiogram prior to Screening that shows no evidence of thromboembolic disease 13. If on the following: vasodilators (including calcium channel blockers), digoxin, spironolactone, or L-Arginine; must be on a stable dose 30 days prior to Baseline and maintained throughout the study 14. If on corticosteroids, has been receiving a stable dose of ≤ 20 mg/day of prednisone (or equivalent dose, if other corticosteroid) for at least 30 days 15. Women of childbearing potential must be using at least one form of medically acceptable contraception. Women who are surgically sterile or those who are post-menopausal for at least 2 years are not considered to be of childbearing potential. Men who are not sterile must also agree to use contraception Exclusion Criteria: 1. Participation in a device or other interventional clinical studies, within 30 days of Baseline and during study participation 2. Participation in a cardio-pulmonary rehabilitation program based upon exercise within 30 days prior to Baseline and/or during the study 3. Has uncontrolled systemic hypertension: SBP \> 160 millimeter of mercury (mmHg) or DBP \> 100 mmHg during Screening 4. SBP \< 90 mmHg at Screening or Baseline 5. History of orthostatic hypotension or at the time of Screening; defined as a drop in SBP by ≥ 20 mmHg or DBP of ≥ 10 mmHg during Screening 6. History of left-sided heart disease and/or clinically significant cardiac disease, including: 1. Aortic or mitral valve disease (stenosis or regurgitation) defined as greater than mild; 2. Pericardial constriction; 3. Restrictive or congestive cardiomyopathy; 4. Left ventricular ejection fraction \< 40% 5. Left ventricular shortening fraction \< 22% by ECHO prior to Screening; 6. Symptomatic coronary disease 7. Significant (2+ for regurgitation) valvular disease other than TR or PR 8. Acutely decompensated heart failure within 30 days prior to Baseline 9. History of atrial septostomy within 180 days prior to Baseline 10. History of obstructive sleep apnea (treated, untreated or resolved) 11. Diagnosis of Down syndrome 12. Moderate to severe hepatic impairment 13. Has chronic renal insufficiency as defined by serum creatinine \> 2.5 mg/dL or has an eGFR \< 30 mL/min at Screening, or requires dialysis 14. Has a Hgb concentration \< 8.5 g/dL at Screening 15. Personal or family history of the following: 1. Congenital or acquired methemoglobinemia; 2. RBC CYPB5 reductase deficiency 16. G6PD deficiency or any contraindication to receiving methylene blue 17. For subjects with HIV any of the following: * Concomitant active opportunistic infections 180 days prior to Screening; * Detectable viral load within 90 days of Screening; * T-cell count \< 200 mm3 within 90 days of Screening; * Changes in antiretroviral regimen within 90 days of Screening; * Using inhaled pentamidine 18. Receiving chronic treatment with prostacyclin/prostacyclin analogue within 60 days of Baseline 19. Requirement of intravenous inotropes within 30 days prior to Baseline 20. The use of oral or topical nitrates (nitroglycerin, glyceryl trinitrate (GTN), isosorbide dinitrate, and isosorbide mononitrate) within 30 days prior to Baseline and until EOS or Termination 21. Known or suspected hypersensitivity or allergic reaction to sodium nitrite or sodium nitrate 22. History of malignancy within 5-years prior to Baseline 23. Other severe acute or chronic medical or laboratory abnormality that may increase the risk associated with study participation 24. Has a disorder that compromises the ability to give informed consent 25. Is currently pregnant or breastfeeding or intends to become pregnant 26. Investigators, study staff or their immediate families