Comprehensive Fentanyl Control Act This bill amends the Controlled Substances Act to modify the drug quantity thresholds that trigger a mandatory minimum prison term for a defendant who manufactures, distributes, or possesses with intent to distribute fentanyl. It also establishes a consecutive mandatory prison term for a defendant who commits a drug offense involving a detectable amount of heroin or fentanyl. The bill establishes a rebuttable presumption that the illegal manufacture of a controlled substance that contains a detectable amount of heroin or fentanyl creates a substantial risk of harm to human life. The Drug Enforcement Administration may temporarily place a drug or substance into schedule I based on a finding: (1) that the drug or substance satisfies the criteria for being a synthetic opioid, and (2) that adding it will prevent abuse or misuse. The bill makes it a crime to knowingly mail to an unauthorized person equipment that may be used to manufacture counterfeit controlled substances. A violator is subject to criminal penalties. Finally, it makes it a crime to import, export, manufacture, distribute, dispense, or possess with intent to manufacture, distribute, or dispense, a synthetic opioid that is not clearly labeled. A violator is subject to criminal and civil penalties.