Qhov tseem ceeb tshaj plaws yog qhov zoo ntawm cov hnab ntim khoom. Cov hnab ntim sib txawv yuav tsum tau siv raws li qhov xav tau ntawm cov pej xeem. Tej zaum lawv yuav muab pov tseg lossis rov ua dua tshiab, uas txiav txim siab lawv qhov zoo. Qhov zoo kuj yog qhov tseem ceeb hauv kev txiav txim siab tus nqi. Ton hnab manufacturers tseem pom zoo kom koj xaiv ton hnab nrog tus nqi siab dua me ntsis, kom qhov zoo tuaj yeem lav.
Cov ntaub ntawv raw ntawm lub hnab ntim kuj yuav cuam tshuam rau kev xa tawm thiab cov nqi muag khoom ntawm lub hnab ntim. Muaj ob hom loj. Qhov zoo ntawm lub hnab ntim khoom tsim los ntawm cov khoom siv raw yuav txawv; nws cov txheej txheem ntau lawm kuj yuav txawv. Txij li cov khoom siv raw siv sib txawv, nws cov txheej txheem ntau lawm kuj yuav txawv, yog li nws cov nqi kuj tseem cuam tshuam los ntawm cov txheej txheem ntau lawm.