Whether you’re looking at a domestic water filter or a water filter for foodservice applications, you’ll likely notice that amongst the technical specifications, each filter has a micron rating. But what does that mean?
What is a micron?
A micron is a metric unit of measurement, also known as a micrometre, a micron is a millionth of a metre or a thousandth of a millimetre. It is denoted with the symbol: μm.
To help give an idea of just how small this is, a micron is about the size of a single grain of milled flour while red blood cells measure approximately 7-8 microns in diameter.
What is micron rating?
The micron rating is the size at which particles are retained by the filter. For example, a five-micron filter will stop particles of five microns or larger from passing through the media. A micron is a micrometre, which is a thousandth of a millimetre. To put this size into context, a human hair is between 40 to 90 microns in diameter, bacteria range from 0.2 to 50 microns and particles above 50 microns can be seen by the naked eye.
When filtering solids from liquids, the smaller the micron rating, the more effective the filter and the greater the number of particles that are removed from the final filtrate.
Micro Rating Chart
| OBJECT | MICRON SIZE |
| Viruses | .01 – .1 microns |
| Asbestos | .08 – .8 microns |
| Paint Pigment | 1 .5 microns |
| Bacteria | .5 – 50 microns |
| Yeast | 2 -15 microns |
| White Blood Cell | 25 – 30 microns |
| Pollen | 10 – 90 microns |
| Pin Point | 75 microns |
| Human Hair | 80 – 100 microns |
| Silica Sand | 100 – 200 microns |
Why does my filter need a micron rating?
Micron ratings in water filters are used to offer guidelines into what size contaminant can be removed from the water. The size of the contaminant determines the size of the micron rating you require, for example if we want to filter out asbestos, we would need a water filter capable of removing contaminants that are between 0.8 Microns and roughly 8 Microns which is the size of asbestos.
A micron rating can be compared to mesh doors in hot countries that are used to allow the air to pass through, but prevents flies, bugs and other unwanted creatures from entering. The principle is the same but instead of mesh there are tiny pores allowing water to pass through but blocking tiny contaminants that can be present in water.
Bearing in mind that most micro-organisms and cysts when in the dormant stage of a micro-organism are above 1 micron in size, a water filter with a rating of 1 micron or lower will physically block them from passing through.
Water filters are designed to remove impurities from water, such as sediment, dirt, sand, and other particles. The micron rating of a filter refers to the size of the particles it can effectively remove. A micron is a unit of measurement that is one-millionth of a meter. Thus, a 0.5 micron filter can capture particles that are 0.5 microns or larger in size, while a 0.2 micron filter can capture particles that are 0.2 microns or larger in size.
The choice of whether to use a 0.5 micron or a 0.2 micron filter depends on the specific application and the quality of the water being filtered. In general, a 0.5 micron filter is suitable for most applications where the water is relatively clean and free of large particles. This may include drinking water, water used for cooking, or water used for washing. A 0.5 micron filter is typically used as a pre-filter to protect more expensive downstream filtration equipment, such as reverse osmosis systems.