"And he shall burn upon it" (Exodus 30:7-8). Resh Lakish said: the fire of Gehinnom has no power over the sinners of Israel. This is argued by a fortiori reasoning from the golden altar, and so forth, as stated above.
How the Golden Altar Shields Israel's Sinners From Gehinnom
Yalkut Shimoni on Torah 385:3
(שמות ל ז-ח) וְהִקְטִיר עָלָיו. אֲמַר רֵישׁ לָקִישׁ פּוֹשְׁעֵי יִשְׂרָאֵל אֵין אוּר שֶׁל גֵּיהִנֹּם שׁוֹלֶטֶת בָּהֶן, קַל וָחֹמֶר מִמִּזְבַּח הַזָּהָב וְכוּ' כְּדִלְעֵיל.