Different kinds of plastic usually. A harder shell, then a softer liner.
Helmets are mostly made from polystyrene
Skateboard helmets were never really invented for the purpose of just skateboarding. The first skateboarding helmets were rudimentary hockey helmets, made by companies like Cooper and Norcon, because there were no helmets made for skateboarding, and these were light and relatively inexpensive. The first helmets made for skaters were probably the Flyaway helmets in the late 1970s. Around this same time, other brands started marketing their existing safety helmets, which could be used for bikes, hockey, hanggliding, or any other activity, directly to skateboarders. Very few companies have made specific safety changes geared at skateboarding during this time. Protec has been the leader in sales of skateboarding helmets, and their design and materials have stayed largely the same over the last thirty years, with only minor tweaks. Several other companies have entered the market, but have not been able to gain a large enough share of the business to maintain longevity. Since skaters, for better or worse, care as much or more about appearance as they do about safety, this trend seems likely to continue.
In world war one, helmets where made of steel, to help protect your head from any bullets or other weapons used (:
Yes if you don't you could fall and crack your head open and go to the hospital!
plastic
A Fireman's helmet is made from metals such as brass, aluminum and nickel. You can get more information about this at the Wikipedia. Once on the website, type "Firefighter's helmet" into the search field at the top of the page and press enter to bring up the information.
Space helmets are usually made of a strong polycarbonate material for durability and protection from the vacuum of space. They also have specialized visors made of materials like gold coating to protect astronauts from harmful radiation and extreme temperatures in space. Inside, helmets have padding and ventilation systems to keep astronauts comfortable during spacewalks.
It is always important to wear helmets when you skateboard, ride a bike and skate. It is for your safety. I prefer everyone to wear it. Some people thinks it looks funny, but the point is to not get hurt right?
The company is Italian but the helmets are made all over the world.
Bicycle riders are expected to fall less often, but with more force than skateboarders. So bicycle helmets are made to soak up more force, and then be replaced after a bad fall. Skateboard helmets are made to soak up less force, but to remain useful even after several falls. Bicycle helmets are also generally made to allow more airflow, to keep the rider's head cooler during hard riding.
Skateboard helmets can be purchased at most sporting good stores like Sports Authority and Dick's Sporting Goods. They can also be bought through websites such as Amazon and eBay.