The thing is, much of the heroin US dealers are selling is cut with fentanyl by the time they get it. They have no idea what they are selling. Illicitly made fentanyl is dirt cheap and made in large quantities. Heroin that comes into this country is already heavily cut or is pure fentanyl sold as heroin. The street corner dealers have no idea.
What is worrisome is that many street pills are also cut with, or pressed from pure fentanyl as well, so those who use opioids in pill form are also at great risk.
Good. That's the way it should be. My son is a heroin addict and the fentanyl scares me more than the heroin to be honest. Most people who die of OD nowadays die because of the fentanyl that's in the heroin, not the heroin itself.