The fresh air inlet to the HEPA filter is NOT under or at the the front bumper! The air inlet is upwards where the Tesla "T" is and the air is guided down and backwards to the filter.
The air under or at the bumper is for cooling purposes of cooling water etc.
Ok so let me clarify what I misstated.
There is some sort of damper near the front bumper that opens/closes based on the recirc mode. There seems to be some air return pathway that goes through there. I should have said that's also where the air inlet is. But that damper clearly helps control where the air comes from.
I think you'll see a lot of conflicting information on this, and if you're observant, you'll be able to confirm that a lot of it is wrong. Many people don't believe that any air comes into the cabin without going through the filter, and many people don't believe that the filter is anything more than a HEPA filter. Because I am allergic to a lot of things and sensitive to a lot of others, I can tell you with very little doubt that plenty of air bypasses the HEPA filter when bioweapon defense mode is off and that bioweapon defense mode seems to remove things that a HEPA filter doesn't (I say "seems to" because I have to admit I'm generally driving at highway speeds, so it is at least somewhat feasible that the positive pressure clears the cabin while the outside source is already out of range). From my observations, I can tell you that bioweapon defense mode seems to activate the compressor even though I'm not sure why that would be relevant. I can also tell you that recirc is forced on when the fan speed is increased to 10 or 11 and that I generally see bioweapon defense mode run at 9 with recirc off. Those observations are on recent software versions (v9+), I don't remember v8 (version where you had more precise control over HVAC functionality and could have only part of the settings [compressor, fan, airflow direction, recirc] be auto vs having auto functionality be all-or-nothing like it is now) well enough to tell you whether or not it was different (part of me thinks it was possible to run fans at 10 or 11 without recirc in v8, and bioweapon defense mode might have used 10 or 11 then; part of me also thinks that it was possible to use bioweapon defense mode without the compressor back then as well, but I don't understand why they would have restricted all of these possibilities later on if the system originally allowed them).
I don't think that bioweapon mode off vs on is somehow intentionally changing where the air comes into the car. My understanding is that the intentional part of the path of air into the HVAC is always through the filter(s), and bioweapon mode additionally achieves a positive pressure in the cabin which prevents/reduces air coming into the car from all the other gaps (because the air wants to push out). My wife says this is how labs and other hepa-certified clean rooms work too.
I have a 2016 X with PUP and bioweapon defense mode. Can anyone help me confirm how the air venting modes work? Any corrections are appreciated.
1) AC on, recirculate on
The inlets under the bumper close, stopping most outside air from entering the cabin. Outside air slowly leaks in to the cabin through the door seals and various cracks. Fans push the air inside the cabin through the AC system, and through the smaller cabin filter, near the glove box.
2) AC on, recirculate off
The inlets under the bumper open, enabling outside air to flow through the huge HEPA filter and into the cabin. If fan speed is set to a lower setting like 5, then air from outside leaks into the cabin through door seals and various cracks (not through HEPA filter). Fans push the air inside the cabin through the AC system, and through the smaller cabin filter, near the glove box.
3) Bioweapon defense mode
Exactly the same as #2 above, but the fan speed is set to high (like speed 9 or 11), so there is positive pressure inside the cabin. There is barely any outdoor air leaking into the cabin through door seals and cracks. Instead, all the outdoor is entering the cabin through the huge HEPA filter.
I would just add that there must be an intentional air outlet in the car somewhere as well. With that in mind:
1) AC on, recirc on: Air that's already in the car goes toward the outlets, outlets are closed, air circles back around to the front of the car near the inlets, which are also closed, and from there through the filters and back around. In the meantime various leaks occur.
2) AC on, recirc off: Outside air is allowed into the inlet path, then through the filters, through the cabin, toward the outlets, and out of the car. Various other leaks occur and I suspect it depends on how fast you are going and other parameters whether those leaks are inward or outward or both. Like when you drive with your trunk open in an ICE car and the exhaust fumes get sucked into your cabin.
3) Bioweapon: I think it's like 2, but some magic happens to positively pressurize the cabin. For instance I speculate the inlets are open, the outlets are closed or partially closed, so air goes in, through the filter, pressure builds up in the cabin, forces its way out through cracks but the positive pressure is maintained because more and more new (outside) air continues to get forced into the cabin
It would be great to get confirmation on how bioweapon actually works.
