From Swann’s Science Vessels. I’m pretty sure each unit can only have one applied to it at a time. However, say you have 3 hybrids close enough to each other and hit all 3, will all 3 be taking damage at 3x the rate?
If it works like SC1 irradiate, which I believe it does, the AoE damage would add up from multiple units with irradiate on them.
I’m not sure if it does but irradiated hellbats are funny when the zerglings run into them and disintigrate to fire and nuclear farts.