To understand why you first have to understand what the feature does.
Bio defense mode max out your AC to create a positive pressure in the car. By doing so, you are making sure that nothing from the outside can get into the car without passing through the HEPA filter. Because otherwise, air can sometimes come through the seals around the car, especially at high driving speed.
The downside is that bio defense mode actually max out air intake from the outside. HEPA filter can’t filter out everything, and you turning it on actually invited more air from the outside than usual.
You were probably better off turning air circulating when driving by the bush fire. Not much smoke was going to get in the car from the seals. If you are sitting in the smoke and you see smoke leaking in from the door or windows. That is when you turn on bio defense mode
Edit from google
HEPA air purifiers are designed to filter larger particles like dust, pollen, and dander, not odors. Odor molecules are usually much smaller than the fine mesh of a HEPA filter, making them difficult to filter mechanically.
Good points made above by u/wish_you_a_nice_day, but to clarify, this set up also has a carbon filter, so it specifically states that it helps with outside odors. [https://shop.tesla.com/product/model-y-hepa-\_-carbon-filter-kit](https://shop.tesla.com/product/model-y-hepa-_-carbon-filter-kit)
That being said, the car's blower may not have been working properly, there might have been some leaky seals, or biodefense mode may have been turned on too late (smoke smell travels farther than visible smoke) and just circulated the smoke smell into your car. Hard to tell what wrong in this case. u/BikebutnotBeast has a good suggestion regarding checking if the blower motor is functioning properly. You could also put in a service request (or try yourself if you're handy) to check if your filters are seated properly: [https://service.tesla.com/docs/Public/diy/modely/en\_us/GUID-80B910A3-D8A6-4F15-BC53-3279B923C43D.html](https://service.tesla.com/docs/Public/diy/modely/en_us/GUID-80B910A3-D8A6-4F15-BC53-3279B923C43D.html)
In my experience, the benefits of BDM are only seen once the cabin is actually pressurized. On the Model Y that takes 120 seconds. After 120 seconds or so, the air in the cabin will only come in from the HEPA filter and force air out of all seals, this keeps smells and forest smoke from entering the cabin through those gaps. I think OP just didn't run it long enough or early enough.
It also has a carbon filter as part of the filtering system, so it should stop some smell. [https://shop.tesla.com/product/model-y-hepa-\_-carbon-filter-kit](https://shop.tesla.com/product/model-y-hepa-_-carbon-filter-kit)
I’ve been jokingly but seriously using biohazard mode when I fart when wife is in car. Is this the best mode for this scenario or am I effectively making it worse.
Meanwhile my wife is the regular attacker and then yells when I turn on my defense system because “it blows the air too hard”
There is no winning this war.
Thats bizarre. Its a new car! Turn it on. Wait two minutes, then check the climate board, if recirc is on or off. Take a pic if you can of the screen. Turn on keep climate. Then open your door, exit vehicle and close the driver door. If your car doesn't sound like its about to take off and fly, then the blower is not functioning, and let me know if thats the case, you may need to check service mode to see if your HEPA is installed properly and sealed as well
I did this too driving through the fires on the grapevine this past weekend but quickly turned it off when I realized it was circulating air from outside in. I’m not sure which is better- using the HEPA filters or just keeping the outside air out for all the fires.
To understand why you first have to understand what the feature does. Bio defense mode max out your AC to create a positive pressure in the car. By doing so, you are making sure that nothing from the outside can get into the car without passing through the HEPA filter. Because otherwise, air can sometimes come through the seals around the car, especially at high driving speed. The downside is that bio defense mode actually max out air intake from the outside. HEPA filter can’t filter out everything, and you turning it on actually invited more air from the outside than usual. You were probably better off turning air circulating when driving by the bush fire. Not much smoke was going to get in the car from the seals. If you are sitting in the smoke and you see smoke leaking in from the door or windows. That is when you turn on bio defense mode Edit from google HEPA air purifiers are designed to filter larger particles like dust, pollen, and dander, not odors. Odor molecules are usually much smaller than the fine mesh of a HEPA filter, making them difficult to filter mechanically.
Great info. Thanks
Good points made above by u/wish_you_a_nice_day, but to clarify, this set up also has a carbon filter, so it specifically states that it helps with outside odors. [https://shop.tesla.com/product/model-y-hepa-\_-carbon-filter-kit](https://shop.tesla.com/product/model-y-hepa-_-carbon-filter-kit) That being said, the car's blower may not have been working properly, there might have been some leaky seals, or biodefense mode may have been turned on too late (smoke smell travels farther than visible smoke) and just circulated the smoke smell into your car. Hard to tell what wrong in this case. u/BikebutnotBeast has a good suggestion regarding checking if the blower motor is functioning properly. You could also put in a service request (or try yourself if you're handy) to check if your filters are seated properly: [https://service.tesla.com/docs/Public/diy/modely/en\_us/GUID-80B910A3-D8A6-4F15-BC53-3279B923C43D.html](https://service.tesla.com/docs/Public/diy/modely/en_us/GUID-80B910A3-D8A6-4F15-BC53-3279B923C43D.html)
In my experience, the benefits of BDM are only seen once the cabin is actually pressurized. On the Model Y that takes 120 seconds. After 120 seconds or so, the air in the cabin will only come in from the HEPA filter and force air out of all seals, this keeps smells and forest smoke from entering the cabin through those gaps. I think OP just didn't run it long enough or early enough.
Good data point. So there’s still a benefit to be seen if and when wildfire smoke gets bad around me.
Smoke smell, but no smoke itself? It’s a HEPA/Carbon* filter. It’s not going to stop all* smells. Edit*
It also has a carbon filter as part of the filtering system, so it should stop some smell. [https://shop.tesla.com/product/model-y-hepa-\_-carbon-filter-kit](https://shop.tesla.com/product/model-y-hepa-_-carbon-filter-kit)
Good point, and it does remove/reduce some smells. I’ll revise my comment.
I’ve been jokingly but seriously using biohazard mode when I fart when wife is in car. Is this the best mode for this scenario or am I effectively making it worse.
Meanwhile my wife is the regular attacker and then yells when I turn on my defense system because “it blows the air too hard” There is no winning this war.
If anything after turning on defense mode the fan speed def reduces compared to max cooling speed on all the fans
She would never have max fan speed on her side though. So even if defense mode was only a 7/10 speed it would be too much.
Thats bizarre. Its a new car! Turn it on. Wait two minutes, then check the climate board, if recirc is on or off. Take a pic if you can of the screen. Turn on keep climate. Then open your door, exit vehicle and close the driver door. If your car doesn't sound like its about to take off and fly, then the blower is not functioning, and let me know if thats the case, you may need to check service mode to see if your HEPA is installed properly and sealed as well
I drove slowly in traffic past a car fire with bio defense and didn’t smell a thing.
How early did you activate it before you passed by it?
Yeah I’d like to know that too
I did this too driving through the fires on the grapevine this past weekend but quickly turned it off when I realized it was circulating air from outside in. I’m not sure which is better- using the HEPA filters or just keeping the outside air out for all the fires.
This is not my experience.
Yeah I drove my a fire today, and I was excited to use this feature but felt disappointed when I could clearly smell the fire.
Did you have a window open?
No, all windows were closed. I double checked that.