Lub raj xa dej muffler yog ib feem ntawm lub cav tso pa tawm.Lub tso pa tawm yog qhov tseem ceeb heev rau kev lag luam roj thiab ib puag ncig.Lub tsheb tso hluav taws xob yuav tshem tawm cov pa phem uas tsim tawm hauv cov txheej txheem combustion.Lub tshuab tso pa tuaj yeem tsis tsuas yog tiv thaiv cov pa phem xws li carbon monoxide, nitrogen oxides thiab hydrocarbons los ntawm kev nkag mus rau hauv lub cab, tab sis kuj "purify" cov roj ua ntej nws tawm mus rau ib puag ncig.

Cov pa tawm muffler yeeb nkab feem ntau suav nrog cov pa tawm manifold, tso pa tawm thiab muffler.Feem ntau, peb lub calibration catalyst los tswj cov emission ntawm lub cav pa phem kuj tau nruab rau hauv lub tso pa tawm.
Thaum cov roj hluav taws xob tso tawm, nws tsis muaj nuj nqis rau lub cav lawm.Cov roj no dhau los ua cov pa hluav taws xob thiab tawm ntawm lub cav.Tom qab tso tawm los ntawm lub tog raj kheej, cov pa pa nkag mus rau hauv cov pa tawm manifold.