Collembola smell with their antennae. On the the antennae are specialised sensilla that can detect air-borne molecules.

Any distinct group of setae or spines is called an 'organ', such as the trochanteral organ in Entomobryidae and Katiannidae, the male ventral organ in some Onychiuridae, the organ of the 3rd antennal segment of most Collembola, the male dorsal organ in Pseudobourletiella spinata itself, etc. In many cases the function of the organ is not yet known.

This group is called 'nasal' simply because it happens to be located at a place refering to the place of our nose...