Комментарий к Охолот 12:2

סרידא (coarse web or matting/stuffed matting used for stoppers of stoves) – like a kind of earthenware lattice-work/grid/mesh. It is the Aramaic translation of (Exodus 27:4, 38:4): “a grating of meshwork”/מעשה רשת – making mesh. And it is smooth and the leftover is outside of the oven a handbreadth from every side.

Netting placed over the mouth of an oven, [so that it is] closed with a sealed lid: If there is uncleanness below [the netting] or above it, everything becomes unclean; But what is directly [above] the air-space of the oven remains clean. The oven referred to here is assumedly a used oven, one which is susceptible to impurity. The netting placed over it is also attached to the oven such that it forms a tightly sealed lid. This means that the inside of the oven cannot become impure. The netting goes beyond the sides of the oven by a handbreadth, as was the case with the board in yesterday's mishnah. As was the case there, the netting is considered to form an ohel over anything below it. If there is a source of impurity below or above the netting, everything found below or above the netting is impure because the netting is an ohel. However, the inside of the sealed oven is not defiled and therefore, anything found above the air-space of the oven is pure. This is the main difference between this and yesterday's case. In yesterday's mishnah even the oven, and anything in it, was impure.

הכל טמא – vessels that are underneath it and that are above it, except from vessels that are on top of it opposite the airspace of the oven, because the tent brings defilement underneath it all around the oven and returns and bursts forth above. But even the defilement that is above bursts forth downwards and it is stretched around and returns and bursts forth above.

If there is uncleanness directly [above] the air-space of the oven, everything directly above it even to the sky becomes unclean. If the uncleanness is above the oven, directly above its air-space, it travels only upwards. Anything underneath the netting or underneath the oven will remain pure.

כנגד אוירו של תנור טהור – for it is surrounded by an airtight seal and interrupts it.

כנגדו עד הרקיע טמא – but what is underneath it is ritually pure.