
Tesla’s ‘Bioweapon Defense Mode’ proving invaluable to owners in CA wildfires - Bud
https://www.teslarati.com/elon-musk-tesla-model-s-x-bioweapon-defense-mode-ca-wildfires/
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vinay427
[https://smartairfilters.com/en/blog/tesla-
mazda/](https://smartairfilters.com/en/blog/tesla-mazda/)

Apparently it may not perform noticeably better (other than in speed of
filtration) than a 2010 Mazda 3 or, even more surprisingly, random Uber cars
in Shanghai and Delhi. I'm unclear how accurate or widely applicable the
results of this test are, however.

~~~
ryacko
It’s just a high quality HEPA filter and a slight overpressure.

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fpgaminer
Slight tangent: Can anyone recommend a decent air quality sensor in the
sub-$100 range? I've been curious lately about measuring PM2.5, VOCs, etc. but
haven't found a good option.

The sensor in the article looks really nice (Twitter thread mentions
[https://www.amazon.com/Digital-Quality-Detector-Tester-
Monit...](https://www.amazon.com/Digital-Quality-Detector-Tester-
Monitor/dp/B07DL1M46J) as something similar. Twitter thread also links the
exact product on Aliexpress, but I refuse to link Aliexpress here since that
site is nearly malware).

But the problem with that sensor and all the other sensors I've found thus far
(HPMA115S0, SDS011) is I can't be sure how accurate at all they are. I'm not
looking for scientific grade stuff here, but if the sensor is off by a factor
of two, for example, it's a bit useless isn't it? Especially if I have no idea
how far off it is.

For example, I found this research paper:
[https://www.researchgate.net/publication/322628807_Developme...](https://www.researchgate.net/publication/322628807_Development_of_a_Calibration_Methodology_for_the_SDS011_Low-
Cost_PM-Sensor_with_respect_to_Professional_Reference_Instrumentation)

If I'm reading it correctly they show that the SDS011 sensor is completely
useless for PM10 measurements. For PM2.5 it can be off by a factor of 2 under
certain conditions. They were able to come up with a calibration formula that
makes it much more accurate (on PM2.5), but I have no way of knowing if their
calibration formula is "universal" for the SDS011 or if the constants would
vary from unit to unit.

And all of those problems on a device that is marketed as being +-15%
accurate. Being off by a factor of two is well beyond 15%...

I haven't dug too deeply yet. Are there better sensors? The HPMA115S0 is brand
name at least, but again I have no way of knowing for sure what its real error
bounds are. Is there some way to calibrate these things at home without buying
an expensive, more accurate sensor (thus defeating the purpose of the cheap
sensor)?

It seems a lot of hobby projects end up using these cheap sensor anyway, even
if they could be completely wrong? Maybe I'm being too picky and an error of
100% isn't a huge deal?

~~~
WestCoastJustin
There was a thread on HN around a week ago around just this topic. Well worth
reading through it "Build a do-it-yourself home air purifier for about $25"
for the comments on filters and sensors. [1].

[1]
[https://news.ycombinator.com/item?id=18445652](https://news.ycombinator.com/item?id=18445652)

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DoreenMichele
"Bioweapon Defense Mode" sounds like a bad choice of name to me. It sounds
like it is trying to intentionally be all B-grade movie dramatic.

If they had named it something else, it probably would have been better
received.

~~~
rdl
Beijing Mode is probably what they really meant, but Bioweapon Defense Mode is
less-bad.

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decafbad
You can't filter lack of oxygen.

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izacus
All you need is to be able to afford a 100.000$ car, nothing else. Then you're
fine even if you've destroyed the air quality.

~~~
berberous
Not that it's still not expensive, but the cheapest model 3 is currently $46k,
which they plan to reduce soon to $35k. Even the current model is effectively
already $36k after tax incentives in some states, and the TCO is even lower if
you factor in gas savings.

~~~
pedrocr
The Model 3 doesn't have this "bioweapon defense mode".

