In the European Union (EU), according to the second basic requirement for construction works of Regulation (EU) N°305/2011 (Construction Product Regulation, or CPR), cables permanently installed in buildings must be classified in terms of their reaction to fire, smoke production, flaming droplets, and acidity. The classification is harmonized at the EU level. Nevertheless, every EU country decides what kind of classification a cable must have to be installed in a specific location depending on its fire risk, following the assumption that the higher the fire risk of the area, the higher the fire performance of the cable. According to CPR, the acidity is indirectly assessed by performing EN 60754-2, giving the additional class based on pH and conductivity measurements. Hydrogen chloride (HCl) is one of the gases PVC cables release when they burn. In some applications out of the scope of CPR, acid scavengers are commonly used in special grade PVC compounds to reduce the emission of acidic smoke. In this first part of the paper, the basic concepts of regulations in the EU on acidity are presented, a review of literature on HCl scavenging is given, and an introduction on acid scavenging at high temperatures is outlined. In the following parts, we will enter more detail about the topic with new data, comparing them with some old ones, mainly from a series of conferences held by some Italian compounders between 2019 and 2022. They were supported in their research and dissemination by PVC4cables, the European Council of Vinyl Manufacturers' (ECVM) platform dedicated to the PVC cables value chain.