How Small Is 0.2 Microns? Understanding the Science Behind LifeStraw Filtration
When we say that LifeStraw filters contaminants from water down to 0.2 microns, it’s easy to recognize that it’s small, but understanding how small that is, is important. A micron, or micrometer, is one-millionth of a meter. To put that into perspective, a single human hair is roughly 70 microns wide. That means the pores in a LifeStraw filter are about 350 times smaller than the width of a human hair. Even when compared to things we think of as microscopic, 0.2 microns is remarkably small. Take red blood cells, for example. These are completely invisible to the naked eye, yet they measure around 6 to 8 microns in diameter. That makes them roughly 30 to 40 times larger than the pores inside a LifeStraw filter.
All LifeStraw products remove Bacteria, Parasites, and Microplastics.
Bacteria, which are often responsible for waterborne illness, are also significantly larger than 0.2 microns. Common bacteria like E. coli typically measure around 1 to 2 microns in size, while others can be even larger. This means that even the smallest bacteria are still bigger than what LifeStraw allows to pass through.
Then there are protozoan parasites, some of the most concerning contaminants in untreated water. Organisms like Giardia and Cryptosporidium range from about 4 to over 10 microns in size, making them dozens of times larger than 0.2 microns. Compared to the filter’s pore size, these parasites are simply too large to pass through.
LifeStraw uses hollow fiber membrane technology, which utilizes mechanical filtration to prohibit bacteria and parasites from passing through. Inside the filter are thousands of tiny, straw-like tubes with microscopic pores. As water flows through these fibers, only particles small enough to fit through the pores are able to pass. Anything larger, including bacteria and parasites, is physically blocked and remains trapped on the outside of the membrane. This process is known as mechanical filtration. It doesn’t rely on chemicals, batteries, or complex processes—just precise engineering at an incredibly small scale.
Nearly all bacteria and protozoa are larger than 0.2 microns, which means they are effectively removed through this filtration process.
What about viruses?
Viruses are smaller than bacteria and parasites, often measuring between 0.02 and 0.3 microns. Because of their size, additional purification methods may be recommended in areas where viral contamination is a concern. LifeStraw also offers products with ultra filtration, purifying water from contaminants larger than .02 microns. These are called “Purifiers” instead of “Filters”. The purification offered by LifeStraw purifiers is 10x smaller than filters (.2 microns vs. .02 microns) which means that the pores on our ultrafilters are 3,500 times smaller than the width of human hair, and 300 to 400 times smaller than an average human blood cell.
Ultimately, 0.2-micron filtration and .02-micron purification utilized in LifeStraw products represents a critical balance of engineering: small enough to remove the most common and dangerous waterborne pathogens, while still allowing water to flow efficiently through the filter. It’s not just about making water look clean, it’s about removing the invisible threats that can cause illness to make water safe. And it comes down to a scale so small, it’s almost impossible to see, but powerful enough to make a life-saving difference.
