Tighter airways mean it is more difficult to inhale and exhale while wearing a mask. The N95 standard is the happy balance between filtration and airflow for humans. N99 and N100 filtration cause more restricted breathing which is not only less comfortable to try to breathe through, but shortens the length of time anyone is willing to wear the mask. If you have your hands on an N99, N100, or HEPA respirator, then you will have excellent protection, but I bet you won't want to wear it for very long.