@Meno- “how does your mask know…,”
Let’s play a game outside with our kids. You need a hose, 2 pieces of cloth folded into at least double thickness (or use a cloth mask), and 4 buckets.
1. Spray water into bucket for 5 seconds.
2. Hold cloth as a shield 1/2” in front of bucket, spray hose so it only hits cloth (not direct into buckets).
3. Hold a piece of cloth half an inch away from the hose (bucket not blocked), and spray through fill bucket for 5 seconds.
4. Now hold 1 cloth like a shield an inch from hose, and another as a shield in front of bucket.
How much water was stopped in bucket 4?
The mask might not stop 100%, but I bet the chances of the bucket filling are much lower.
And that’s why both sides need masks.