Look at the Mission Rebirth in Black Ops you play as "Mason" whit the company of "Reznov", you can be spotted as Mason and Reznov will say: You have been spotted!. But Reznov is Mason so he may no longer been spotted, When "Reznov kill Steiner Mason in the interrogatory say: I swear for god that´s how Steiner died, Reznov killed him in rigth of front of me! Actually Mason is Reznov, how he could do it if Reznov was Mason when killing him!?
Mason wouldnt die of Nova 6 in the chamber because Reznov is out beacuse Reznov is Mason. If Mason would had been Reznov (playing as Reznov) everything will make sense but as Reznov died at Vorkuta it doesent have anything to do there. If Reznov is damaged he wont say anything but it still appaer blood possibly meaning that "Reznov" is knifing himself.