Based on the mass production technique to fabricate 2D materials developed by our group, efficient gas sensors against NOx with sensitivity of 100 ppb are successfully demonstrated. In comparison to international competitors, our products exhibit superior sensitivityselectivity. Furthermore, the technique would be extended to other 2D materials to fabricate various gas sensors against multiple target gases. The integration with internet of things would then open new feasibilities for early monitoring in environmental pollutionhuman safety.