For solo day races such as Quest Glendalough and similar races, the basic equipment is a bike (helmet + puncture repair kit), trail running gear ( shoes, good lightweight jacket ) and small waist / back-pack. You will also need a basic first aid kit, whistle and emergency foil blanket. For the majority of adventure races in Ireland, the kayak and equipment for the paddling section of the course will be provided by the event organisers. There will usually be a mandatory kit list up on all race promotion websites for participants, so it is important to always check that.
For team based adventure races, you will usually require a mountain bike and most of the same outdoor gear. Race map, compass and map case and map board is also usually required for the navigator(s) on the team. As team based races are usually longer, there is often a need to have some extra clothing, lights and food. Again, all race websites will have detailed lists of mandatory and other race specific kit requirements.