It's an air purifier I believe. Mine has a button on the dash with the same symbol. When mine is on it lights up blue, which I assume means "cleaning" mode (as per the colour of the label). I also assume a green light on mine means the Ioniser is working (don't recall if I've ever seen lit up green though). It's a button that only has on/off, so no options to switch between "Clean" and "Ion" - I assume it changes modes automatically if it needs to.

My car manual is in Japanese, so not much help.

i do not have any button to turn it on / off. it just shows me on the display there.

But what i noticed on mine is that, when my ac was running, the "Clean" did not show up. since it stopped working, it shows.

Also my ac just stopped blowing air, it shows all turned on in the gauge but no air in any vents.

have booked for checkup tomorrow.

There will be a filter hidden up under the glove box somewhere, in most cases they are user replaceable. Not sure what the lifespan is but they are a maintenance item. 

If it's a Nissan (March?) then you have a plasmacluster ion generator installed.

mclean:

 

If it's a Nissan (March?) then you have a plasmacluster ion generator installed.

 

Its a Nissan Tiida 2005 model

It's a branding icon used by Sharp

http://www.sharp.co.jp/plasmacluster/factor/

scroll down and you'll see list of industries they've cooperated with, including your Nissan car

The grape bunch with Ion at the top is the Sharp trademark.  The ioniser usually has two operating modes, called CLEAN and ION or something similar.  When you turn on the AC it goes to CLEAN mode, and when it thinks the car smells nice it changes to the other mode.  CLEAN mode is supposed to neutralise any odours, ION mode it's meant to make you feel good. I don't think there's any filter associated with the ioniser, although the car might still have a separate cabin air filter somewhere.

mclean:

 

The grape bunch with Ion at the top is the Sharp trademark.  The ioniser usually has two operating modes, called CLEAN and ION or something similar.  When you turn on the AC it goes to CLEAN mode, and when it thinks the car smells nice it changes to the other mode.  CLEAN mode is supposed to neutralise any odours, ION mode it's meant to make you feel good. I don't think there's any filter associated with the ioniser, although the car might still have a separate cabin air filter somewhere.

 

I'll have to remember to keep an eye on mine and see of it ever changes mode, I've never really paid that much attention.