Filtering effectiveness: It’s all about microns!

The micrometer or micron (μm) is unit of length equalling 1×10⁻⁶ metre, which is one millionth of a meter or one thousandth of a millimeter. Here are examples of some micron sizes:

• A red blood cell is typically 8 μm.
• A width of a strand of spider web silk is typically 3 – 8 μm.
• A white blood cell is typically 25 μm.
• A human hair is on average 70 μm.
• A grain of table salt is approximately 100 μm.

A micron rating for a water filter indicates the ability of the filter to remove contaminants by the size of the contaminant’s particles. The higher the micron number the larger the filtration pores.

Bacteria range in size from 0.2 to 2 microns in width or diameter and from 1 to 10 microns in length for the non-spherical specie. The common Escherichia coli (E. coli) is a rod-shaped bacterium where each bacterium measures approximately 0.5 μm in width by 2 μm in length. Vibrio cholerae (Cholera) is also a rod-shaped bacterium, measuring 0.3 μm in width and 1.3 μm in length. Viruses are typically 0.004 to 0.1 microns in size, which makes them about 100 times smaller than bacteria.

Bearing this in mind, one should seek a filter with a smaller micron number for better filtering capability; the larger the micron number, the less effective the filter in removing health threatening contaminants.

Removal Rates: