Zevachim 12:5-6

Zevachim 12:5

Regarding the bulls and goats that are burned on Yom Kippur, if they are burned properly, they are burned in the place of ashes (outside Jerusalem) and they render garments ritually unclean. If they are not burned properly (i.e., they were disqualified), then they are burned in the Beis Habira (a location on the Temple mount) and they don’t render garments ritually unclean.

Zevachim 12:6

When they were burned properly, they were carried on poles. If the people carrying in front passed the wall of the courtyard (so they were outside) but those in the rear had not yet gone out, then those in front render garments unclean but those in the rear don’t until they go out. If they have all gone out, then they all render garments unclean. Rabbi Shimon says that both those in the front and those in the rear only render garments unclean once the fire has engulfed the greater part of the sacrifices. Once the flesh of the sacrifices has been charred (which concludes the burning), one who burns it further doesn’t render garments unclean.