Objective: To study the protective effect of hydrogen inhalation on the lungs of sanitation workers exposed to haze. Methods: In this randomized, double-blind, placebo controlled clinical trial, 96 sanitation workers living in Shijiazhuang urban area were recruited during January to February, 2016. All enrolled participants were randomized to 2 groups; the treatment group inhaled H2∶O2 mixture (66.67%∶33.33%) 1 hour per day for 30 days, while the control group inhaled N2∶O2 mixture (66.67%∶33.33%) 1 hour per day for 30 days. Respiratory symptoms were evaluated and fractional exhaled nitric oxide(FeNO), biochemical indexes, lung function were measured at baseline(the 0th day) and during treatment (the 8th day, 15th day, and 30th day). Results: (1)The FeNO levels of the treatment group (16±5)×109 were lower than those of the control group(21±14)×109 on 8th day of treatment, with significant difference(F=6.94, P<0.05). (2)The levels of FEV1 were significantly higher in participants from the treatment group as compared to the control group on both 8th [(96±13)% vs(94±14)%(F=3.96, P<0.05)] and 30th day [(97±14)% vs (95±12)%(F=8.5, P<0.05)] of treatment, while PEF was also increased on 15th day [(73±15)% vs(67±18)%(F=8.68, P<0.05)]. (3)The sputum levels of MMP-12 and SOD3 were consistently lower in the treatment group as compared to the control group at each time point, and the levels of IL-10 were higher in the treatment group as compared to the control group on the 15th and 30th day. MDA and IL-2 levels were lower in the treatment group than in the control group on the 30th day(P<0.05). The sputum levels of CRP and TGF-β1 at each time point were not different between the 2 groups (P>0.05). (4)The serum levels of IL-2 and SOD3 were lower in the treatment group as compared to the control group while IL-10 was higher than in the control group at each time point, and MMP-12 was lower in the treatment group than that in the control group on the 30th day(P<0.05). The relative ratios of CRP, TGF-β1 and MDA in serum at each time point between the 2 groups were not significantly different (P>0.05). (5)Hydrogen inhalation improved respiratory symptoms such as cough. Conclusions: Inhalation of hydrogen gas could alleviate airway inflammation and oxidative stress of sanitation workers exposed to air pollution. There was even a significant inhibitory effect on the level of systemic inflammatory response. Importantly, inhalation of hydrogen could improve respiratory symptoms such as cough.