Firewalls are more complicated than you might think. They don’t just separate the passenger compartment from the engine area of a car, they do a few other things as well. They help to keep cool air in the vehicle and reduce noise. They are also designed to channel frontal impact energy around the passenger compartment rather than through it. They are also a key component in preventing dislodged engines from entering the passenger cabin during a collision.
In a modern car, a firewall is made up of pressed sheet metal and is welded to the adjacent panels that make up the vehicle chassis. Classic cars typically have a firewall pad that is made of fiberglass or fiberboard with insulation coating it. These firewalls have numerous openings in them to allow necessary pipes, wires etc from the engine bay to pass through them. It is important to check the firewall pads in classic cars regularly for rust and holes.
The firewall in an automobile was originally invented by Henry Ford to prevent the spread of flames, fumes and smoke into the driver’s cabin in the event of an engine fire. He understood the importance of protecting the lives of his customers and his product.
Today, the auto industry does not regulate firewalls and there are no minimum standards for what is called “firestopping” to protect occupants in the event of an engine fire. Even worse, many items that are used in the average automobile to seal penetrations in a firewall act as accelerants when they ignite.