The day I picked up my wondrous Tesla, I noted I felt nauseous with the air conditioner on. The delivery specialist knew what it was: the ioniser. Sure enough we switched off the function in the controls and the nausea went away. In the recent heat as my city moves to summer, I noted the same feeling. I looked for the function to see if the ioniser had accidentally been turned on during a software upgrade, instead the setting had disappeared. I contacted Tesla, and it turns out that because people picked one setting and kept it there, they just took the control away and kept it at the last known setting. In my case, they're double checking the setting. Interestingly, I learned that the ioniser was included in the classic nose Tesla cars only. For the facelifted vehicles and with the move to the HEPA filter, Tesla removed the ioniser.