Generally speaking, if you're within 15 METERS of a grenade going off in the open.. you're out of the fight no matter what.
Either you're deaf, blind, traumatic brain injury, broken ribs/chestbone from the concussive blast, burned badly, or the shrap has gone straight thru any various parts of your body. Hence, the often used 15 foot rule.
If you're in an enclosed environment, say a room.. you're dead/out of the fight either way for the same and more reasons.
In airsoft, we limit it to 15 feet usually, which is mostly down to just scaling RS down to airsoft standards I'd presume.