It's not a requirement. The reason many vipassana guides say to breath through your nose is because most people can easily feel the air at the tip of nose and i

It's not a requirement. The reason many vipassana guides say to breath through your nose is because most people can easily feel the air at the tip of nose and it gives them a clear point of focus. You can breath through your mouth too. Some people prefer focusing on air coming into the stomach instead. When I have a cold or some other build-up in my nose, I just breath through the mouth, no problem.