Smoke and/or the acrid smell of burning wires -- these are not sensual assaults to be ignored when you're heading down the highway. Just like in Monopoly: Do not pass go, do not collect $200. Drive directly to the shoulder of the road and turn off the ignition.
In the automotive world, smoke does not necessarily mean fire. Depending on the age of the vehicle, it could be steam from the radiator, often caused by a broken fan belt or overheated engine. The simple fact is that if your vehicle is smoking or putting off odors, something's gone wrong.
A significant percentage of smoking vehicles leads to serious consequences. According to statistics from the American Automobile Association and the National Fire Protection Association, 266,000 car fires were reported in 2004, resulting in 520 deaths. Of those fires, 75 percent were caused by bad maintenance, rather than by auto accidents. So first we'll deal with avoiding fires, and then what to do if that smoke does mean fire.
An early indication of a problem is a fuse that blows more than once. The source of the triggered fuse could be either a faulty component or a wiring problem. Both issues can be dangerous and should be resolved.
Next, check for oil leaks and always use a funnel when adding oil. Oil spilled on a hot exhaust manifold can cause a fire.
If you have a gas station attendant add oil, double check that the cap is on securely. This sounds obvious, but better to check than end up with oil all over your engine compartment at best, or an engine fire at worst.
Also, include a check of the fuel system in your regular maintenance schedule. Electrical and fuel system or problems are the major causes of car fires.
Another source of exhaust-related fires is the catalytic converter, the cylindrical unit located in the exhaust pipe, forward of the muffler (which is normally slightly larger in size). Catalytic converters are so hot they can ignite dried grass directly under the parked vehicle.
The first response to a suspected vehicle fire is to pull over, immediately. Fire feeds off oxygen and even slow forward motion will force air into the engine compartment, basically stoking the fire. Exploding cars are generally the stuff of crime dramas, but it's still best to stop in an area away from buildings and people, if you have that option. Burning plastics and other materials can produce toxic gases -- maybe not as visually exciting as an explosion, but it is best not to expose yourself or bystanders.
Next, get yourself and passengers out of the car. However, the following recommendations about trying to put out the fire may seem contradictory, and what you do is dependent on the availability of a fire extinguisher, your ability to use it and your knowledge of auto mechanics.
From personal experience, the two times smoke billowed around my engine compartment, I was fairly sure there was no corresponding fire. One was a broken fan belt, the major clues being a voltage gauge that had flatlined and a temperature gauge that headed toward the danger zone. The other was a little bit of smoke accompanied by a scary reading on the oil gauge (a gas station attendant hadn't replaced the oil reservoir cap after topping it off). I didn't call 911; I called for a tow. If you're not sure what's going on, call 911. Better safe and embarrassed than very, very sorry.
Some sources discourage trying to put the fire out on your own. One thing is certain: An emergency is not the time to start reading the instructions on your fire extinguisher. Everyone should have a fire extinguisher easily accessible in the passenger compartment, and one rated ABC for all types of fires is the best.
If the fire is relatively small and in the interior, use your extinguisher. (Closing the doors and windows may also smother the fire.) If there's a small amount of smoke coming from under the hood, pop the release but don't lift the hood. Quickly spray through the gap, from several feet away, aiming at the base of the fire rather than the flames. The logic is based on the fact that fire feeds off oxygen and lifting the hood can turn a little fire into a large one, instantly. If the fire is large or located in the rear of the vehicle, near the gas tank, your chances of safely extinguishing it are small.
While explosions from car fires are rare, the true danger is the toxic fumes. Another consideration is a vehicle equipped with gas shock absorbers or gas struts. Under intense heat both can explode and turn into lethal projectiles.
That's a lot to remember, so if you forget everything else, as smoke is billowing out of your car, just remember to pull over, turn off the ignition, get everyone out of the vehicle and call for help.