I was reading Mishnah Tamid, studying up on the daily sacrifices in the Temple, and I was happy to see some discussion of the Altar Fire. While I mention this tractate once in my book, it provides some great details when read at greater length. It is describing temple ritual procedures that would have been current in the last iteration of the Second Temple right before the Romans destroyed it as remembered in Jewish oral tradition.

First, it describes priestly procedures for clearing out the ashes from the Altar:

He [a priest] whose lot it was to clear the Altar of ashes went to clear the Altar of ashes, while they said to him, ‘Take heed that thou touch not the vessel before thou hast sanctified thy hands and feet in the laver; and lo, the firepan lies in the corner between the Ramp and the Altar, on the western side of the Ramp’. None went in with him and he carried no lamp, but he walked in the light of the Altar fire. They neither saw him nor heard the sound of him until they heard the noise of the wooden device which Ben Katins had made for the laver; and then they said, ‘The time is come!’ He sanctified his hands and feet at the laver, took the silver firepan and went up to the top of the Altar and cleared away the cinders to this side and to that, and scooped up the innermost burnt [cinders] and came down again. When he reached the pavement he turned his face to the north and went some ten cubits to the east of the Ramp. He heaped the cinders together on the pavement three handbreadths away from the Ramp at the place where they throw the crops of the birds and the ashes from the inner Altar and the Candlestick. (m. Tamid 1.4 [Danby, p. 583])

More on the ashes:

They began to heap up the ashes above the ash-pile, and the ash-pile
was in the middle of the Altar; sometimes there were about three hundred
kors [of ashes] upon it; and at the Feasts the priests did not clear away the
ashes since they were an adornment to the Altar: [when the ashes remained]
it was never through negligence of the priest to clear away the ashes (2.2)

Second, it describes the placing of new wood on the fire:

3. They began to bring up faggots to set in order the Altar fire. Were all
kinds of wood valid for use in the Altar fire? Yea, all kinds of wood were
valid for use in the Altar fire save only olive-wood and the wood of the vine;
but their custom was to use only boughs of the fig-tree or the walnut-tree
or of oleaster-wood.
4. He set in order the greater of the Altar fires to the east side; and
its fore side was to the east, and the inner ends of the faggots touched the
ash-pile, and there was a space between the faggots through which they set
fire to the kindling-wood. (2.3-4)

Thirds, it describes how there were actually multiple fires on the Altar and explains how they had different purposes relating to the incense, and the animal sacrifices:

5. They chose from thence fine pieces of fig-tree wood wherewith to set in
order the second fire appointed for the incense, over against the southwestern
corner, but distant four cubits to the north of this corner; [on weekdays they took wood sufficient to give] about five seahs of cinders, and on the Sabbath sufficient to give about eight seahs of cinders, for there they used to put the two dishes of frankincense that pertained to the Shewbread. Then they put back on the fire the members [of the animal offerings] and the fat pieces that had not been consumed since the evening. (2.5)

The details embedded in these rather abstruse paragraphs are significant: we see how the ashes were dealt with; we learn how the incense to be placed on the shewbread was heated on the altar before being placed; and we see how some animal sacrifices would need to burn for a long time. The multiple fires would need to be tended frequently with new firewood and with ash-clearing. And for what it is worth, 300 kors would be 1,548 bushels. That’s a lot of ashes!