Shopper Will this filter out:
1. Bacteria
2. Chemicals / Toxins
3. Protozoa
4. Viruses
?
STEVE D The MSR AutoFlow Gravity Filter is an excellent backcountry tool. It quickly processes water, and is very simple to use. In North America, bacteria and protozoa are the most common challenges. This unit handles them, as well as sediment. The carbon component of the MSR filter will remove a great deal of chlorine and some VOCs (volatile organic compounds). Removing viruses requires more stringent filtration. If use in developing nations is planned, there are are other filters that would be advisable, such as a unit from Sawyer. For all use other than virus removal, the AutoFlow is awesome.
KATHLEEN P These hollow fiber filters will filter out particles larger than 0.2 microns, which include bacteria, protozoa, dirt, rust, etc. Viruses, however, are too small for most filters to remove - you would need to add a purifying solution AFTER filtration to kill any viruses. (You generally don't have to worry about viruses in the water in North America and Europe.) It also will not remove chemicals dissolved in the water - you would need a secondary filter like activated carbon to do that. (In general, you wouldn't have to worry about dissolved chemicals in backcountry situations.)
I have been using mine for almost 3 years and have never had a problem with it. On backcountry trips it provides the only water treatment needed.
Hope this helps!