Intox nose-only exposure unit

How does the Intox nose-only exposure unit work? How “nose-only” is it?

This was used by [http://www.citeulike.org/group/13793/article/7465836 Divangahi et al. Eicosanoid pathways regulate adaptive immunity to Mycobacterium tuberculosis.Nature immunology, Vol. 11, No. 8. (11 August 2010), pp. 751-758]