Hlau ntug kev ncig yog txheej txheem ntawm kev tshem cov ntse lossis burr npoo los ntawm cov hlau uas los tsim kom muaj qhov chaw du thiab nyab xeeb. Cov tshuab tua hluav taws xob ruaj khov yog cov tshuab nce uas tau cog cov hlau uas lawv tau pub dhau, tshem tag nrho cov swb hnyav kom sai thiab ua tau zoo. Cov tshuab no siv cov kev sib tsoo ntawm cov menyuam sib tsoo thiab txhuam kom tsis txhob sib zog dhau los ntawm cov txheej txheem hnyav tshaj plaws.
