Kev faib cov twj ntsuas valve raws li cov khoom siv

Raws li cov ntaub ntawv siv hauv kev tsim cov twj paj nruag, nws tau muab faib ua: cov khoom siv hlau ntsuas li qub, cov khoom siv tsis yog- cov khoom siv hlau, thiab cov khoom siv hlau valve lub cev hauv ob sab phlu ntsuas li qub.