There are quite big differences between the European recommendations and those listed by ASHRAE. One major reason is that ASHRAE requirements are minimum code requirements, where the basis for design is adapted people, while the European recommendations are for un-adapted people (visitors). Adapted people are considered those who entered a room and are already acclimatized to the situation in the room, i.e. approximately 15 minutes after entering a room. Visitors are people who just entered a room and are assessing the situation in the room at that moment of entering.
Picture shows the required ventilation rates from standard EN15251 compared to ASHRAE 62.1.