Idea on how to be sure if your mask is protecting you effectively

First step, get your mask on

Second, get a lighter or even a match will do

Third, while your mask is on your face, put the fire on which produced by lighter or match then try to blow it up while wearing your mask and see if it will wipe or not.

Depending on how your blow will impact the fire is the inefficiency of your mask. So, it's better if the fire will not move despite how strong you blow it while wearing a mask.

Let's help each other by staying safe! Let's defeat this virus!