The odor gets on clothes and hair. I can tell when my customers are stoned, mask or not. It blocks some of your green breath, which I thank you for. But the general odor of cannabis is unmistakable. How you smoke is the best way to not be known you just smoked. Smoking outdoors in a well ventilated area, then using a mask is far better than hotboxing your car then slapping a mask that’s been sitting in all that smoke on your face.