This is s very difficult thing. Different people using different product, there's tolerance, experience, internet ego, all mixed together.
There are ways that experienced people can make good, educated guesses about product purity and such, but it takes time and ah, research.
There's comparison to pills. One can compare how sniffing 1 or 2 bags compares to how many milligrams of various pills. If you've had experience with variety, with education and common sense, you can make better estimates. Then things like the look, the taste, the drip, etc.
Fentanyl has certain different feels. Experienced users can tell the difference, but it's difficult if its mostly heroin with a little fent mixed in.
I have a friend that needed a comprehensive blood test. He was a daily iv user and used a variety of product from around this very big East coast city. O fent showed up and i know that it was tested for. I can only say that for now, at least with some of the main stamps in this major city, fent has not made its way in. This may be another testament to the very controlled stamp bag system.
There are ways that experienced people can make good, educated guesses about product purity and such, but it takes time and ah, research.

There's comparison to pills. One can compare how sniffing 1 or 2 bags compares to how many milligrams of various pills. If you've had experience with variety, with education and common sense, you can make better estimates. Then things like the look, the taste, the drip, etc.
Fentanyl has certain different feels. Experienced users can tell the difference, but it's difficult if its mostly heroin with a little fent mixed in.
I have a friend that needed a comprehensive blood test. He was a daily iv user and used a variety of product from around this very big East coast city. O fent showed up and i know that it was tested for. I can only say that for now, at least with some of the main stamps in this major city, fent has not made its way in. This may be another testament to the very controlled stamp bag system.