An unavoidable side-effect of forced induction is that compressing air raises its temperature.[1]:70 As a result, the charge density is reduced and the cylinders receive less air than the system’s boost pressure prescribes. The risk of detonation, or "knock", greatly increases. These drawbacks are countered by charge-air cooling, which passes the air leaving the turbocharger or supercharger through a heat exchanger typically called an intercooler.