Ntau cov dej haus ntawm kev ua lag luam tau pib siv cov hwj yas yas raws li cov khoom ntim ntim ntim, tab sis qee cov khoom lag luam yog tsim nyog sivIav FwjRaws li cov khoom ntim loj, tshwj xeeb tshaj yog rau cov khoom siv npias. Qhov zoo ntawm cov iav fwj yog raws li hauv qab no:

1. Cov fwj iav tuaj yeem siv ntau dua, uas tuaj yeem txo cov nqi ntim;

2. Cov iav iav muaj kev nyab xeeb thiab huv, muaj cov zoo corrosion, thiab muaj cov txiaj ntsig kev ua haujlwm, thiab muaj peev xwm ntxuav tawm ntawm cov kub thiab tuaj yeem khaws cia ntawm qis kub. Haum rau cov tshuaj acidic (xws li txiv hmab txiv ntoo thiab kua txiv qab zib, thiab lwm yam) ntim;

3. Cov iav muaj peev xwm hloov xim thiab pob tshab dua yooj yim;

4. Vim tias lub khob iav yog tsim nyog rau kev siv ntawm kev siv cov kab ntau lawm, ntau yam kev txhim kho iav tsis siv neeg, siv cov iav fwj ib qho kev sib tw loj hlob;

5. Cov khoom siv iav muaj cov teeb meem zoo, tuaj yeem ua tau zoo heev los tiv thaiv cov khoom yaig thiab lwm lub sijhawm tuaj yeem tiv thaiv cov tshuaj tsw qab sab hauv lub khob iav volatile tshuaj rau cov cua.