If you break down the SteriPEN's name, you basically have the concept in a nutshell. The SteriPEN has the physical appearance of a pen and it sterilizes water. That's pretty straightforward, right? But what's amazing is how the SteriPEN rids water of those pathogens we learned about earlier. The key is ultraviolet light.
Ultraviolet light is energy-rich, electromagnetic energy naturally emitted from the sun. And while it can also have many adverse affects (this is why we wear sunscreen), when introduced to contaminated water, it destroys the ability for bacteria and viruses to reproduce. Once the DNA or RNA in virus or bacteria absorbs the UV light, it can no longer reproduce, effectively killing the organism and making it harmless to the human body.
The mechanics of the SteriPen are simple: It has a long, clear wand that lights up similar to a neon or fluorescent tube light. The wand on the end of the SteriPEN's body allows the UV light to transmit into the water. Each SteriPEN model works the same way. The small mechanical body produces the UV light and the wand captures and disperses it throughout the water. Each SteriPEN has a cleaning cycle and times vary depending on the model.
It's important to understand that while UV light sterilizes water; it doesn't remove bad odors or tastes as chemicals or carbon filtration would. The best possible solution for water purification would be a combination of sediment and particle removal followed by carbon filtration and then UV light sterilization. This gadget won't rid your water of any funky smells or coloration. You can use chemicals and carbon filters for that. But the SteriPEN will kill the bacteria that give you travelers diarrhea such as E. Coli so you won't get sick while you travel.
Now that you understand the mechanics of the SteriPEN, let's move on to some of the features and get into how to use it.