According the the SteriPEN website, "SteriPEN products use ultraviolet (UV) light technology to purify water, destroying more than 99.9 percent of bacteria, viruses and protozoan cysts such as giardia and cryptosporidia.
The method has now been used for over one hundred years, and is currently used to purify drinking water by some of the largest cities in the world, including Seattle, New York (scheduled soon), Tempe, AZ and many others in North America, Europe and Asia. Ultra Violet light is also used by leading bottled water manufacturers to purify their source water."
I've had this SteriPen for a number of years but had only used it sporadically. I didn't need it on my 2010 wilderness trip to northern Canada because up by the Arctic Circle you don’t need to treat your water. In the BWCA however it is the recommended practice and I choose to use the SteriPEN and was glad I did. I like this model because it takes readily available AA batteries. My NiMh rechargeable batteries lasted nearly two-weeks of treating over a gallon of water a day. I had heard stories of Steri-PENs not being dependable but we had no problems and I would recommend this as the most convenient method of treating water that I've ever used. The only negative aspect is that it is a fairly delicate item and needs to be given special care. I don't know if it would hold up to the rugged use an outdoor program might give it. What's your experience?
FINAL EVALUATION: Excellent! This meets all the criteria for a great backcountry product.
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To see the evaluation criteria click HERE