A worker picks out unqualified medical N95 masks at a mask production company in Shenyang, capital of northeast China's Liaoning Province, Feb. 8, 2020. For days, the company has pledged continuous work of up to 20 hours per day to ensure the daily output of over 20,000 medical N95 masks, which will be supplied to the novel coronavirus epidemic prevention frontline of Hubei and Liaoning Provinces. (Xinhua/Yao Jianfeng)