The blood of sacrificial animals was poured out at the altar’s base, and it is likely that some kind of conduit existed for carrying the blood away from the temple area. Herod’s temple is reported to have had such a conduit connected with the SW horn of the altar, and in the rock of the temple area, an opening has been found that leads to an underground channel going out to the Kidron Valley.

Sanctification and use of tabernacle altars. At the time of the installation ceremonies, both altars were anointed and sanctified. (Ex 40:9, 10) At that time, as also in subsequent sacrifices of certain sin offerings, blood of the sacrificed animal was put upon the horns of the altar of burnt offering, and the rest was poured out at its base. (Ex 29:12; Le 8:15; 9:8, 9)

Annually on Atonement Day the altar was cleansed and sanctified by the high priest’s placing some of the sacrificial animals’ blood on the horns of the altar and by spattering it seven times upon the altar.​—Le 16:18, 19.