There are employees of the Dutch Council for Refugees present in the COL, POL and the Application Centres (AC).
Asylum seekers who are detained during their border procedure do have access to (other) NGOs (such as Amnesty International) and UNHCR. These organisations are able to visit asylum seekers in detention as any other regular visitor, but in practice this hardly happens. On the one hand, asylum seekers are not always familiar with the organisations and do not always know how to reach them. On the other hand (representatives of) the organisations do not have the capacity to visit all the asylum seekers who wish to meet the representatives of the NGOs or UNHCR.
There are also so-called voluntary visitor groups which visit asylum seekers in detention.