Comment by dmlorenzetti | Hacker News Reader

Comment by dmlorenzetti | Hacker News Reader

Bioweapon Defense Mode is not a marketing statement, it is real.

Their filter does a good job cleaning particles out of the cabin air. Good on them.

Nevertheless, calling it "Bioweapon Defense Mode" is clearly a prize bit of marketing. A system designed to protect against an external bioagent wouldn't run huge amounts of outside air through the filter. That would just load the filter more quickly, impacting its performance (for chemical agents) and/or its energy requirement (for particles). Instead, you would cut the outside air intake as much as you could get away with, in order to buy the occupants time to drive clear of the plume.

Since they claim that the car is responsible for the decrease in the particle concentration in the test chamber, they must be running a pretty high flow of ambient air through the system. Of course, the ambient concentration would decrease even without the car's filter, due to particle deposition, and possibly due to losses in the sampling instrument. But then you only report those other loss rates if you're interested in science, rather than in marketing.

I disagree, and I can tell you from first hand experience that this is how a tank NBC protection system works - The crew cabin is pressurized with high flow of filtered air.

http://elbitsystems.com/Elbitmain/files/Kinetics_NBC-CBRN.pd...

[Edit - adding this] I can also say, that this creates a very uncomfortable sensation in your ears while the cabin is being over-pressurized (about 2 minutes)

Yes but it's the positive pressure that's important, not the high flow rate. You may need a high flow rate to maintain whatever pressure you're aiming for but the thing that's keeping out any contaminants is the fact that every tiny leak is only going to have air going from the inside to the outside other than the filter itself. If you've got a big room with only one tightly sealed door, you don't need a lot of flow to keep out any contaminants.

Thing is you can't maintain positive pressure in a battletank without high flow rate. Tanks are not fully sealed.

Are they not? Many tanks can traverse rivers driving on bottom with special attachment to the main hatch. Leopard 2 does that.

As this sounded intriguing, here's a video I've found of this: https://www.youtube.com/watch?v=C26rJiOnKLk.

It appears the tank commander needs to guide the driver on directions, though...

It also appears that the tank is not waterproof, as you can see quite substantial leaking at around 30 seconds in.

Correct. The commentary says it's equipped with 2 water pumps to remove whatever leaks through.

I guess that's German engineering for less-than-perfect road and maintenance conditions. I like the redundancy too!

Learn something everyday, quite surprising that solution with pumps was even considered and that it actually safe for crew and tank internal systems.

That's the most practical solution. A tank is not a space capsule, sealing a multi-ton rotating turret is unrealistic.

I think the idea is though that the car air is already compromised. e.g. they have opened the doors to get into the car, then closed the doors and enabled the BDM.

It needs to filter the air from outside and get it into the car to quickly displace the air already inside the vehicle that is contaminated.

At the point where the air is clean though it would be a good idea to make the car it's own little safe haven and allow the occupants to drive to safety (hell it could even drive itself to safety if it can sense when the air is safe again outside)

It needs to filter the air from outside and get it into the car to quickly displace the air already inside the vehicle that is contaminated.

In exactly the same way that recirculating air from inside the vehicle is easier on your air-conditioner, recirculating interior air is easier on the filter.

With the A/C, you want some minimum outside air to get rid of CO2 and whatever other effluents the passengers and materials in the car are generating. But if you were driving through a plume of toxic gas/particles, you wouldn't mind smelling your armpits and a little extra CO2 if it meant extra protection from whatever is out there.

Hence I believe that if you were really designing a Bioweapon Defense Mode, you would cut the intake of outside air to an absolute minimum. You might not go for zero flow, because you might want to pressurize the cabin a bit (in the U.S., most building mechanical systems are set up this way). But I wouldn't expect to cycle through enough outside air that you could halve the concentration in that bubble (which is probably 10-20 car volumes or more) in less than 15 minutes, as their graph shows.

That would depend on your definition of a "bioweapon". How many people have to be killed by a toxic substance injected into the air to consider it a weapon? 1.2 million people died in China alone in 2010 from air pollution.

http://www.nytimes.com/2013/04/02/world/asia/air-pollution-l...

Weapons are defined by intent, not body count.

Criminal negligence doesn't require intent. If you fire your gun into the air because you are a jackass, and the bullet comes down somewhere and kills someone, the gun is still a weapon, even though you had no intent to kill.

I think he meant the intent of the creator of the compound/item.

A gun is created to kill. A taser to incapacitate. A knife is created to cut/stab things - and since human flesh is highly cuttable substance even kitchen knives are considered weapons. A car is created to transport people but can be used to kill. Cars are not weapons because in their conception there is no intent to harm someone.

What about a rock? The same analogy holds true. Anything can be a weapon, its simply absurd to contend that intent matters.

There has to be intent in there someone. A gun is a weapon. A rock can be a weapon. A dangerous polluting factory may be criminally negligent and morally despicable, but it's not a weapon unless it was deliberately deployed to maximize exposure to a target group. (Which isn't out of the question, given human nature, but I haven't heard of any evidence for it happening yet.)

What if we replace the gun and bullet with a bottle rocket? Is it a weapon now?

1.2 million premature deaths, not outright deaths. These will be people about to die anyway who died slightly sooner than otherwise. Car crashes kill people 50 years ahead of schedule, not 1 year.

It is not a bioweapon. It is chemical weapon. Quite the different beast.

That's kinda the point of the article. Not only does it purify contaminated air for the occupants, it actually reduces contaminants outside the car. Tesla is marketing this to locales with literally dangerous levels of smog.

Don't think its the filter that they're referring to as BDM, it's positive cabin pressure. Or at least, the combination.

I agree, however how else could they charge god knows how much for a $50 hepa filter?

its not like its new technology. It doesn't say how long the filter lasts, and crucially the failure mode for the filter. (will it bypass when its full? do you get a warning? etc etc etc )

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