How do you check whether a supplier's PCF is usable?

Check four things: the standard it was calculated under, the life cycle boundary, whether a third party verified it, and whether the figure sits in the expected range for that product type. For a service footprint, add a fifth: that the functional unit matches how you buy the service. PACT alignment is a useful proxy for completeness, since it lists the fields a PCF should carry. DitchCarbon's PCF Evaluator grades an inbound PCF or EPD on exactly these points and gives a verdict on whether it can enter a calculation.