Mishnah 4 in Chapter 11 continues with the exact same topic. The Mishnah states that there is no practical difference regarding what material the item upon which the chatas blood splashed is made of:
"Beged" - a garment made of natural fibers.
"Sak" - a coarse fabric woven from goat hair.
"Or" - a sheet of leather.
The rule is that the material is not the determining factor: as long as it is an absorbent material that can be washed, one is obligated to wash it in its specific manner and with those same cleaning agents, and in a holy place - since this is the language of the verse, and the intent is the Azarah of the Beis HaMikdash.
From here the Mishnah transitions to a new topic - kashering vessels:
That same verse we mentioned earlier also deals with the obligation regarding cooking kodashim - and for now we will speak about the chatas - in a pot, a pan, or a jug. Here the matter of nosar enters the picture: when the allotted time passes, and for a chatas this means the following morning, the meat becomes nosar and is forbidden. That is to say, if the chatas was slaughtered on Tuesday afternoon, at dawn on Wednesday the meat becomes nosar. A problem thus arises that can be termed a kashrus problem: nosar is not kosher at all, and there is a liability of kareis for eating it. Therefore, it is incumbent upon a person to kasher his vessels.
The novelty of our Mishnah is that even the kashering of those vessels must be done in the Azarah, and this is because the verse requires it - from the very next verses, those same verses dealing with the blood of the chatas that we have been discussing all along.
The source of the obligation in the verses:
Verse 20 states that any food that touches the meat of the chatas attains its status, meaning that it too will become invalid as nosar after the allotted time. The verse continues: if some of its blood splashed on a garment, the place of the splash requires washing "bemakom kadosh" - in a holy place. The Torah means the courtyard surrounding the Mishkan, and the halachic parallel for this is the Azarah of the Beis HaMikdash.
The verse following it begins with a letter "vav" connecting it to the preceding one, and two laws are stated in it:
Earthenware vessels - if chatas meat (and similarly other kodashim) was cooked in it, the vessel requires breaking. The reason for this is that there is no possibility of kashering an earthenware vessel through hagalah, immersing in water, or the like, since it does not expel all of its absorbed flavors, and therefore it must be destroyed.
Metal vessels - if the meat of the korban was cooked in a metal vessel, and "nechoshes" means copper or bronze (and apparently even a cast iron pot is included in this), the vessel requires "merikah ushetifah" - scouring and rinsing: scouring is a sort of purging, and rinsing in water.
Since that same verse begins with a "vav" and comes immediately after the preceding verse, which deals with a garment being washed inside the Azarah, the understanding is that the kashering of the vessels that absorbed what became nosar - whether through scouring and rinsing or through breaking - must also be done inside the Azarah.
And this is the language of the Mishnah explicitly: the breaking of the earthenware vessel must be done inside the Azarah, "bemakom kadosh" - in a holy place, and likewise the scouring and rinsing of the metal vessels, literally the copper or bronze vessels, must be done in a holy place - which is the Azarah.
The precision of the word "**Zeh**":
From the wording of the Mishnah "**Zeh**" - this, the Gemara deduces, and Rashi explains similarly, that the obligation of washing is unique to a chatas alone, and is stricter in it than in other kodshei kodashim, such as an asham and an olah: if their blood splashed onto a garment, there is no obligation to wash it in the Azarah, whereas for the blood of a chatas, there is such an obligation. However, it appears that with all sacrifices, and certainly with kodshei kodashim, if they were cooked in a pot, or if fat remained in a pot and the like - after the allotted time, once the meat becomes nosar, the vessel requires kashering: removal, scouring and rinsing, or breaking, each according to its respective rules.
In summary: In this Mishnah, we learned that the obligation of washing does not depend on the material of the article - a garment, a sack, or hide - and any absorbent material requires washing in a holy place, in the Azarah. Likewise, we learned the law of kashering vessels that absorbed the meat of sacrifices that became nosar: an earthenware vessel through breaking, and a metal vessel through scouring and rinsing, and from the juxtaposition of the verses and the conjunctive vav, it emerges that these actions too are performed inside the Azarah. Finally, we focused on the precision of the word "**Zeh**" - this, from which we learn that the obligation of washing is unique to a chatas, while the law of kashering vessels applies to all sacrifices.