Greenstone 2022

[rich]

https://www.nps.gov/isro/upload/ISRO_We ... r_2022.pdf

[dcclark]

I notice that the water purification recommendation is the same as last year, but I hadn't noticed the distinction between "Physical Purifier" (apparently OK on its own) and "Water Filter" (should be combined with chemical or UV treatment).

I got pretty confused trying to understand the difference, so I figure I may as well share here what I figured out. The tl;dr is that a "physical purifier" can filter much smaller particles, meaning it can filter out viruses (in addition to bacteria and protozoa). For example, the "physical purifier" can filter particles down to 0.02 microns, but the "microfilter" can only filter down to 0.2 microns (10x larger).

I found this, more or less, in this article from MSR, but they also seem to be a bit confused. They even link to the MiniWorks EX using *both* the term "physical purifier" and "microfilter". I think that calling the MiniWorks a "physical purifier" is a mistake, since it only filters down to 0.2 microns. Only the "Guardian" model is a physical purifier in the sense above.

[backwoods doc]

The first article seems designed to prepare folks for overcrowded campgrounds. I guess that's fair.

[Midwest Ed]

I found this, more or less, in this article from MSR, but they also seem to be a bit confused. They even link to the MiniWorks EX using *both* the term "physical purifier" and "microfilter". I think that calling the MiniWorks a "physical purifier" is a mistake, since it only filters down to 0.2 microns. Only the "Guardian" model is a physical purifier in the sense above.

I agree the MSR Specs and marketing are confusing. They are clear in the definitions, Purifier includes removal (99.99%) of viruses while Filter does not.
Yet, while one of their Purifiers (called Guardian) has the smaller filler size (0.02 micron), the other (called MiniWorks EX Purifier System) has just the "normal" 0.2 micron Filter plus carbon. But the unit called MiniWorks EX Microfilter also has just the 0.2 micron filter plus carbon.

My first thought was the carbon was different between the 2 MiniWorks. But then the word System caught my eye. Upon further inspection, I noticed the System had several packets of purification tablets laying at the base of the Purification system. Also, the tail end of the description mentions the included tablets.

The only time I (personally) am worried about viruses in water is when there as any risk the water was drawn near or down stream from human or animal activity. This would be in populated areas from rivers with treated or untreated sewer run off possible. That can be almost anywhere in populated areas. In wilderness areas the concern is accessing water close to or downstream from an outhouse, not very likely on The Island although Daisy Farm while flooding comes to mine. Other extremely questionable sources would be a puddle (on or off the trail) or a beaver pond.

Viruses are very tiny. This graphic might help but remember they generally don't float around or exist alone at their native size. When they are in water they are attached to to much larger droplets of water. A 0.2 or 0.4 micron filter will remove a goodly number but there's no guarantees so always (especially when in doubt) take the extra precaution.