Piv nrog cov tshuab nqus tsev ib txwm siv, kev lim dej tsis yog nplua nuj heev, tsis zoo li cov khoom siv tes tuav thiab kab rov tav lub tshuab nqus tsev. Thiab nws yuav tsum tau ntxuav tom qab siv txhua zaus. Yog tias tsis tau ntxuav, nws yuav yooj yim tsw ntxhiab thiab xeb. Los ntawm cov xwm txheej no, nws muaj teeb meem ntau dua. Qhov zoo ntawm lub tshuab nqus tsev nqus tsev vacuum ntawm lub khw tsis sib xws, thiab tus nqi sib txawv yog qhov loj, thiab nws nyuaj rau cov neeg siv khoom sib txawv.
