Does anyone know what the position between 0 and 1 on the fan control **** is for?

 

I think it opens the vent to let outside air flows in.

The fan is off at that position, but you can feel air coming in on freeway speed.

 

It is not in the operators manual but I think jackei is correct. I feel a slight draft when moving but no fan noise when I select the '.' (dot) position. My Ford Explorer has an 'off' position also but it's manual suggests not using it because it shuts off ALL outside venting and can lead to inside fogging. They say to use it only when you want to temporarily prevent an oder from getting inside (passing by the turkey farm on shipping day for example).
This may be true with the xfire also, no outside venting at all with the switch in the off position.