As we have learned (on daf 83, and on yesterday’s daf, as well) animals that are appropriate for sacrifice will become fully sanctified if they are brought onto the altar – or onto the ramp leading up to the altar – even if there is a problem that would, ordinarily, cause them to be disqualified for sacrifice.
The Gemara on today’s daf raises the following question: Does that rule apply to the air above the altar? If an animal that is disqualified from sacrifice is placed above the altar, does it also become sanctified to the extent that it cannot be removed from the altar and must be sacrificed?
In response to this question, the Gemara points out that the same law of keivan she-alu, shuv lo yerdu – once they were elevated onto the altar, they cannot be brought down – applies not only to the altar, but to the ramp leading to the altar, as well. If the air above the ramp does not have the same level of holiness as the ramp itself, then how could such a sacrifice be transported to the altar? Once the kohen lifted it off of the ramp, he would have abrogated the rule that once the animal reaches the altar, it cannot be removed from it! Clearly the air above the altar has the same status as the altar itself.
The Gemara rejects this proof by arguing that the kohen might have to drag the animal up the ramp, keeping it in physical contact with the ramp at all times.
In response, the Gemara points out that there was a gap between the ramp and the altar, and the kohen would surely need to lift the sacrifice at that point in order to transfer it from the ramp to the altar. This, too, is rejected by the Gemara, which argues that the gap was small enough that at all times the majority of the sacrificial animal was either on the ramp or on the altar.
The Gemara’s conclusion is that the air above the altar – and the ramp – has the same status as the altar itself, a position accepted by the Rambam as the halakha (see Rambam Mishne Torah Hilkhot Pesulei HaMukdashin 3:12).