Lub npe tshuaj rau cov dej khov qhuav yog cov pa roj carbon dioxide (CO₂), uas yog tsim los ntawm kev ncaj qha desublimation ntawm gaseous carbon dioxide nyob rau hauv tej yam kev mob ntawm kev kub siab thiab tsis kub. Nws muaj qhov kub tsis tshua muaj siab heev-kwv yees li -78.5℃-uas yog qis dua li 0℃qhov kub ntawm cov dej khov zoo tib yam. Nyob rau hauv chav tsev kub, cov dej khov qhuav tsis yaj rau hauv cov kua; Hloov chaw, nws nkag mus rau sublimation, hloov ncaj qha los ntawm cov khoom mus rau lub xeev gaseous. Cov yam ntxwv no ua kom ntseeg tau tias nws tawm tsis muaj kua seem thaum thauj thiab khaws cia.
Cov dej khov zoo tib yam, qhov sib txawv, yog cov khoom siv dej (H₂O), tsim thaum cov dej khov ntawm qhov kub qis dua 0 degree. Nws qhov kub thiab txias feem ntau hovers nyob ib ncig ntawm 0 degree, thiab thaum melting, nws reverts rau cov kua dej. Txawm hais tias cov dej khov zoo tib yam muaj peev xwm ua kom txias tsis muaj zog, nws cov khoom siv dav dav thiab tus nqi qis ua rau nws muaj kev xaiv rau kev ua kom txias txhua hnub lossis luv luv - lub sijhawm khaws cia.
