[derbOac]

My impression is that the concern with EV and battery fires is that they can occur in the home or while otherwise stationary, unexpectedly causing much more catastrophic damage. ICE fires, in contrast, seem to be mostly associated with collisions, or somewhat less so with driving; it seems uncommon for ICEs to suddenly catch fire in an enclosed building.

e.g., https://www.jstor.org/stable/44631649

I'm not an expert on this though, and these are just my general impressions, which is maybe the point of the article. On the other hand, it doesn't seem to address the nature of EV fires in a scientific, public-health kind of way.

I think the thing most people are concerned about is a question like "how likely is my car to cause my house to burn down just sitting in the garage, while I'm sleeping?" Maybe the answer to that is the same with ICEs and EVs but that's the question that needs to be addressed.

[vel0city]

ICE fires aren't often related to collisions. I've seen a neighbor's house burn down due to a car that had been parked in their garage for hours combusting. I've had multiple ICE cars recalled for catching fire when stopped. In the examples in the articles they mentioned vehicles in parking garages and on cargo ships, those weren't moving.

Your general impressions don't reflect reality. Out of all the cars I've owned my ICE ones have been way more likely to burn down my house while sleeping than my EV. Your own article even starts off with "most occur in motor vehicles not involved in collisions."

[dataflow]

> I've seen a neighbor's house burn down due to a car that had been parked in their garage for hours combusting

The ICE car combusted while the engine wasn't running? Like, it was parked, they'd turned off the car as usual, and hours later it randomly combusted? Do you have any information on what the likely cause may have been? (e.g., hot weather? unexpected sparks?)

[Kirby64]

Yes. Usually it's related to some sort of electrical fire that occurs when the vehicle is off, that catches fluids (brake fluid, gas, etc) on fire, although a big enough regular electrical fire can do it too.

Here's an article on a recall Hyundai/Kia are going through right now: https://fortune.com/2023/09/27/hyundai-kia-recall-nearly-3-4...

They're recommending you park the vehicles outside and away from structures.

[dataflow]

Fascinating, thanks.

> the anti-lock brake control module can leak fluid and cause an electrical short, which can touch off a fire while the vehicles are parked or being driven.

> [...] Dealers will replace the anti-lock brake fuse at no cost to owners.

How can replacing a "fuse" prevent fluid leakage?!

[vel0city]

Sizing the fuse to be smaller means the fuse will blow faster at the short before the wires in the puddle of brake fluid get hot enough to start the fire. Chances are the fuze was oversized to begin with.

[dataflow]

I figured about as much, but I guess my point was: shouldn't they be fixing the leak?! Would people even know about the leak otherwise? Or is this going to silently surprise/kill people when their ABS fails?

[squarefoot]

> Do you have any information on what the likely cause may have been? (e.g., hot weather? unexpected sparks?)

Possibly one of the above plus gasoline vapors which are a lot more dangerous and explosive than gasoline itself and can be easily ignited by a spark not necessarily due to a short circuit.

[XorNot]

There's an entire 12V electrical system which stays active. There's also rubber and plastic parts, possible contaminants, a bevy of additives...plenty of interesting chemistry which normally does nothing but in the right sequence of unlikely events leads to an ignition.

[dataflow]

> There's an entire 12V electrical system which stays active. [...]

I'm not that illiterate about cars or basic physics. I was trying to figure out what actually went wrong in their situation. Because I'd never heard of any specific cases of these actually happening. Previously these sounded incredibly less likely to me than what I'm now discovering here.

[vel0city]

I don't remember the specifics about that situation. Something melted and slowly leaked and eventually caught fire. I don't think whatever happened in that case rose to become a recall. It was a relatively new Cadillac in the mid 1990s IIRC. I was a kid at the time it happened.

But yeah, vehicle fires happen to parked cars all the time. As mentioned I've had multiple cars have "don't park in the garage" kind of recalls, one car has even had multiple (Hyundai). In the article posted above it opens with:

> WHILE SOME FIRES in motor vehicles occur as a result of collisions, most occur in motor vehicles not involved in collisions. These non-crash-induced fires are relatively frequent (one for every 1,000 registered vehicles) but in general are less hazardous to occupants and bystanders than crash induced fires.

It later states:

> They occur on an average of one out of every 1,000 registered vehicles and can result in significant property damage

https://www.jstor.org/stable/44631649

[dataflow]

Thanks!

[marcosdumay]

To be fair, ICEs tend to cath fire while they are moving. That's the time every system in the car is most stressed.

That means the odds of it catching fire on your garage while you sleep are lower.

EVs by their turn are highly stressed while charging.

[Kirby64]

The way I see it, ICE vehicles have a different potential fire mechanism that isn't present in EVs.

Since ICE vehicles operate at much hotter temperatures, they inherently have a combustion potential due to leakages (brake fluid, gas, oil, etc). It's pretty common to have a bit of smoking from a fluid change, purely from accidental drips (even a little bit). If it's a continuous drip and hot enough areas such as exhaust, you can get a fire.

EVs just don't have anything that hot during normal operation. The operating temperature of both the electric motors and the batteries is much much lower than the temperature of engine operating temps (usually 200+F) or exhaust gas temperatures (something ridiculous like 1200F on catalytic converters, and 500F on exhaust piping).

[vel0city]

> ICEs tend to cath fire while they are moving.

This is not backed by any evidence while the opposite is shown in the referenced paper. Most ICE fires happen when parked according to actual data.

[organsnyder]

My PHEV vehicle (Chrysler Pacifica Hybrid) had a recall that caused fires while parked. It turned out to be related to part of the 12v system.

[DannyBee]

ICE fires occur in stationary as well. It's just that we have learned to handle gas better over the years.

I otherwise agree, but it's complicated because while what you say in the first sentence is true, it was true for ICE at one point too.

So for example, this is why gas containers have pressure releases, etc.

I mean, for an ICE vehicle you go to a gas station and fill it up. It's hard these days to think about how really dangerous that is because of how safe we'd be able to make it. It's much more dangerous than charging an EV car in theory.

Even storing the gas is dangerous!

That said, what you are pointing out is that the other difference is more around the mechanism. Gasoline can't ignite as a liquid. At high temperature it just vaporizes quickly into a gas and then ignites :)

As a gas, it has a lower explosive limit of about 1.5% and an upper of about 7.5%. Within that concentration level it is flammable. Outside of it, no.

Because you can get it to combust within this range, and we've become good at avoiding this happening in "normal" circumstances through safety mechanisms developed over the years.

This was not always true, and you saw more fires in lots of situations as a result.

EV fires on the other hand are usually self-sustaining chemical reactions[1] that got out of hand. Once triggered, they result in fire unless some safety mechanism stops them.

You can see this is really not dissimilar from ICE - we spend almost all energy/safety mechanisms on preventing the ability to cause a fire in the first place.

However, that said, these chemical reactions are more "omnipresent" than ICE for sure - once they are both "off", EV vehicles are more likely to explode than ICE ones.

A lot of this is the fact that they are not really "off" most of the time.

Regardless, however, we will do the same thing we did for handling of gas in general - we will figure out how to make that safer.

If we can make hand-filling your gas tank with an explosive fuel safe i've got faith we'll be able to make EVs sitting around doing nothing safe. We actually already can, just not at the energy density we want yet :)

[1] I understand that as a nitpick, so is burning gas, but let's leave this alone at this level :)

[zdragnar]

This is a lot of words to say that EVs are currently more dangerous than ICE vehicles to park in a garage.

[thebruce87m]

There are no statistics to back up this statement. All we know is that both EVs and ICE car’s spontaneously combust on rare occasions. There are examples of both here: https://normantaylor.com/blog/which-cars-catch-fire-the-most...

What’s interesting to me is that most people talk about NMC batteries in EVs, but from what I can tell LFP batteries should be safer and are becoming more popular. Would be good to see if there are stats to back this up.