Fentanyl overdoses are now the top cause of death among U.S. residents ages 18-45, surpassing suicide, car accidents and COVID, according to an analysis of federal data by opioid awareness organization Families Against Fentanyl. To prevent such deaths, FentCheck’s co-founders and a team of volunteers regularly visit a network of businesses in Oakland, San Francisco, New York and Philadelphia to replenish stocks of the test strips.