Will I OD on Salvia Extract if I vaporize it?

I want to smoke salvia and I have smoked it before. But, I want to vaporize it... Is that a safe way to smoke it? It will be Purple Sticky Salvia, which is the extract right? I am wondering if I get a lower strength extract and vaporize it will I OD or anything. I don't want to die, or get brain damage. Can anyone recomend what strength I should get? thanks