Yeah, from my experience you will probably get sick and start puking well before overdosing. It would be difficult to easily overdose from smoking.
Smoking too much too quickly always made me puke, even with tolerance. Partly due to the taste and other alkaloids in black tar.
HOWEVER, you need to test for fent. If there is fent in your dope ignore what I just said, as this throws everything out the window.
I never really needed more than 3-4 hits to get pretty damn high from the tar I used to get...