Disabling Damage Flash?

[Chryyz]

Revenant told me it was possible, but that he couldn't remember the command. I've been browsing cvars and haven't seen anything that would relate to this. Also, if it's possibly to merely modify the opacity or something, that would be preferred.

Does anyone know the command?

To clarify what I'm talking about, it's the red flash on your screen whenever you take damage.