2,617. Must One Re-Cover Blood?
Hilchos Shechita 14:7
If someone covered blood and it gradually got uncovered, he need not cover it again. If blood got covered by the wind, one need not cover it, but if it subsequently got uncovered, then he must do so.
Hilchos Shechita 14:8
If the only blood present is the lifeblood that sprayed and the blood on the knife, one must cover it.