Car on Fire - Causes and Possible Methods of Prevention

[Wrichik Basu]

TL;DR Summary

Number of cars are catching fire all of a sudden on roads. This thread is for discussion on the causes and methods of prevention.

This is a picture that was published today in our local paper:

This is not the first time a car has gone up in flames. A number of cases have been reported where cars moving on roads have, all of a sudden, blazed up. In a significant number of such cases, the people inside breathed their last as they couldn't escape.

There was no collision. The cars are from different companies, so you can't blame any single company to have produced defective models. All the owners/their close relatives have added that the cars were regularly serviced by authorised personnel. And there is a equal spread between petrol and diesel variants.

The question that arises is, what can cause these flames? In most cases, the car has been burnt so very badly that forensic studies have been unable to recover any good evidence that might indicate the cause of the fire. Short circuit? Engine failure (thereby spreading of the fire from engine cylinders to fuel tank)? From air-conditioning system? What are your guesses?

Of course, once we agree upon some possible causes we can discuss how to prevent such fires.

 

[Greg Bernhardt]

Are they electric?

 

[berkeman]

what can cause these flames?

Here is a good link, with a link to the NFPA website:

https://www.kelnerlaw.com/blog/2017/10/5-common-causes-of-car-fires.shtml

 

[Wrichik Basu]

Are they electric?

We have only a handful of electric cars here. Those are either on petrol or diesel.

 

[anorlunda]

Cars have always caught fire. Media reports are a poor way to identify trends. Do you have actual statistics showing an increased rate of fires?

 

[russ_watters]

...they are easily googlable.

 

[Wrichik Basu]

Cars have always caught fire. Media reports are a poor way to identify trends. Do you have actual statistics showing an increased rate of fires?

Recently, almost every month there is one such incident as per newspapers. But here is a thread started back in 2008, talking over the same issue. On page 14, you'll find a number of pictures. It shows that fire in cars is perhaps a known issue from quite some time.

I was thinking of buying a small powder type fire extinguisher for our car.

 

[AZFIREBALL]

If you are thinking about using a powder type fire extinguisher to save your car, you are barking up the wrong tree. Once you spray that stuff on your car’s motor you might as well give it up as a lost cause. The powder may put out the fire but, you will have a very hard time cleaning up the mess it leaves behind. Cleaning the motor will cost more than the car is worth. Consider using a CO2 extinguisher.

 

[russ_watters]

Recently, almost every month there is one such incident as per newspapers.

There's far more than that, but either way that is insufficient for evaluation. PLEASE look up some statistics and consider the real risk. When your life depends on it, a vague feeling from newspaper articles is not the way to evaluate risk.

 

[anorlunda]

If you are thinking about using a powder type fire extinguisher to save your car, you are barking up the wrong tree.

That's good advice. I always buy foam extinguishers rather than powder. They do not earn A, B or C ratings for reasons I don't understand. But they have the overwhelming advantage that my wife and I would not hesitate to use them for even a minor fire. The other types of extinguishers offer many reasons to hesitate, and hesitation is very bad.@Wrichik Basu , if I remember correctly from my days in fire fighter training, New York City alone reports 27000 vehicle fires per year. Significant would be a jump of 2000/year.

 

[Wrichik Basu]

There's far more than that, but either way that is insufficient for evaluation. PLEASE look up some statistics and consider the real risk. When your life depends on it, a vague feeling from newspaper articles is not the way to evaluate risk.

Nope, I didn't find any good stats. Maybe no one has done statistics on this based on my city.

@Wrichik Basu , if I remember correctly from my days in fire fighter training, New York City alone reports 27000 vehicle fires per year. Significant would be a jump of 2000/year.

That could be a good approximation, but the fact is, I am more interested in causes and preventions. If it has to happen to our car, it will happen and won't be affected by statistics.

If such incidents are quite common, there must be established methods of their prevention. For example, @berkeman mentioned some good causes, but I think I cannot control most of them. If the coolant overheats and the car doesn't show the malfunction indicator, then I will certainly not know about it when I'm driving the car. The best I can do is to device a temperature sensor that can inform me if the temperatures are exceedingly high.

 

[essenmein]

That's good advice. I always buy foam extinguishers rather than powder. They do not earn A, B or C ratings for reasons I don't understand. But they have the overwhelming advantage that my wife and I would not hesitate to use them for even a minor fire. The other types of extinguishers offer many reasons to hesitate, and hesitation is very bad.

A, B and C are ratings for the types of fire, A is things like paper/trash/wood etc, B is burning liquids/gasses, C is energized electrical fire. So a foam type extinguisher would only be good for class A and some B, since it has liquid to make the foamy (usually water) makes it a poor choice for oil or electrical fires, in fact it can make both of them way worse!

I only know this right this minute because just refreshed fire safety lol.

(note that the classifications differ slightly between countries)

CO2 is a good option for no clean up, just have to be aware of its limitations.

 

[essenmein]

Nope, I didn't find any good stats. Maybe no one has done statistics on this based on my city.

That could be a good approximation, but the fact is, I am more interested in causes and preventions. If it has to happen to our car, it will happen and won't be affected by statistics.

If such incidents are quite common, there must be established methods of their prevention. For example, @berkeman mentioned some good causes, but I think I cannot control most of them. If the coolant overheats and the car doesn't show the malfunction indicator, then I will certainly not know about it when I'm driving the car. The best I can do is to device a temperature sensor that can inform me if the temperatures are exceedingly high.

OK so couple of things first, in general, vehicle safety (incl fire) has been steadily improving to the point where we are talking in ppm, the goal is for those numbers to start to be ppb.

Then, OEMs are extremely acutely aware of the fire issue and its repercussions on public perception, they have been for as long as I've been in the industry, so much so, when discussing for example DFMEA for a product, you cannot even say "fire" as an outcome if you want any possible business, the acceptable term is "thermal event", we all know what it means, you just can't say "fire".

In terms of causes, I would say electrical would be the highest (esp with modern vehicles), second would be fluid leaks onto hot parts (eg oil leak onto exhaust manifold, brake fluid on hot rotors, injector leaks etc).

The problem is not a T=0 failure, but at T=10years of corrosion, thermal shock and salt spray that breaks formerly insulating things, sealing things and allows them to conduct just a little bit, or leak a little bit. This was already a challenge with 12V systems, now imagine holding those kinds of reliability requirements for 600V dc...

 

[essenmein]

I bet you HMC's bosses were spitting tacks and looking for people to fire seeing that image on the front page.

 

[Ketch22]

A couple of things to bring up as I am a late arriver on this thread.
First, the incidence of vehicle fires. You would have to show that the increase of fires is greater than the increase of number of vehicles on the road. The evidence that I have seen is that when corrected to an incidence per 100,000 vehicle rate for instance, that vehicle fires are on the decrease. I would like to see any data that you can show.

Second is the fire extinguishers. The dry powder is almost definitely a write off of the vehicle. Foam is a good alternative it does have a liquid base, however the foam makes it less dense than the automotive fluids and it will rise to the surface this (with good coverage) prevents reignition. It is the agent of choice for most liquid fires. CO2 works very well but is a hazard to life and does not prevent reignition once it is dissipated and oxygen is returned to a hot fuel.

Third is the Fire in Question. Modern engines either gasoline or Diesel are almost exclusively Fuel injection. It does not make a difference if they are port injection, Direct injection, Common Rail, Mechanical injection, or composite types. All modern engines (except for carbureted historic units) have a pressurized fuel delivery. It is most common that the fire is caused by pressurized fuel creating a fine spray which impinges on a hot surface. Very common is damage due to impact, this is somewhat abated by inertial switches turning off the fuel pump at a set impulse level. Also common is lack of maintenance where pressurized components rupture due to lack of scheduled maintenance. This can only partially be abated by better materials and better controls in detection. Last in known occurrence is the random failure due to poor materials or design.

Short of creating an "aircraft style" program to aggressively determine cause on a case by case basis I do not think we can really create a definitive cure. Your thread is a good question and may warrant some exploration. I would tend to believe that the effective rate is on the decline and is only an anomaly due to media attention but would love to see further investigation.

 

[Charlie Cheap]

Having built Street Rods/Customs for 50 years, I have seen my share of engine fires. The basic ABC powder extinguishers worked well when I had to use them, and cleaning the motor was not a problem. Burnt wires were a pain! Make sure the engine is OFF before shooting the powder though. I think maybe the FI higher pressures may be cause to think fires are more common, but I have no proof. I am still a carb guy...and I run POINTS. I know, I know, move into the 21'st century Chuck. But points work just as well as HEI up to about 5,000 RPM, and I stopped racing in 1969 when my modified chevy powered 40 Ford coupe with 4-speed got beat by a Hemi powered station wagon.

 

[Tom.G]

https://www.statista.com/statistics/377006/nmber-of-us-highway-vehicle-fires/Shows approx. a 12% DECREASE in U.S. vehicle fires from 1980 to 1993 (from 456 000 to 402 000)

This, from https://www.usfa.fema.gov/downloads/pdf/statistics/v19i2.pdf
shows:
...62 percent of highway vehicle fires originated specifically in the engine, running gear, or wheel areas of the vehicle...

That's just two of over 12 000 000 finds with:
https://www.google.com/search&q=vehicle+fires+statistics

Cheers,
Tom