uhm dangers....
chasing smack isnt very good for the lungs.. yeah.. well... id guess thats mostly because of cuttings. sugar, paracetamol, etc.
in case of tar it might be over acidified (strong smell etc). so you would likely inhale a decent amount of acetic anhydride too, which leads to symptoms like:
"conjunctivitis, lacrimation (discharge of tears), corneal edema, opacity, photophobia (abnormal visual intolerance to light); nasal, pharyngeal irritation; cough, dyspnea (breathing difficulty), bronchitis; skin burns, vesiculation, sensitization dermatitis"
so it might be a good idea to dissolve your stash in just enough water to make it liquid, add sodium bicarbonate in small amounts until no bubbles are being formed and neutralize the anhydride.
also i wouldnt heat it with a blow torch or something but GENTLY, just enough to let it cook, not fry.
its also suspected to cause brain damage. (probably also cuz of burned/heated cuttings)
how to convert tar into a pretty pure freebase, suitable for smoking
there are this rumours about poisonous aluminium on the foil... i dont believe in it but its better to use a glass oil pipe instead. this way its easier to inhale all the fumes anyway and you can heat it more gently.
its lossy as fuck. even in freebase form. some pal here smoked 3 grams within 24h without tolerance. yeah its pretty bad shit around here but 3g would still last a couple of days when snorted.