Everything you need to know about HEPA filters
What is HEPA?
HEPA is an acronym of High Efficiency Particulate Air and is used to describe fiters that are capable of removing 99.97%
of particles that are 0.3 microns (a human hair ranges from 20 to 180 microns in diameter). This standard was introduced
by the US governemnt in the 1950's and has become the standard globally.
HEPA filters are the most common type found in air purifiers and are now also often used the clean the exhaust air from vacuum cleaners.
Typically the filters are made from strands of fibre glass arranged in a random pattern.
How they work
MERV Ratings
In the late 1980's the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) devised a method to rate the effectiveness of air filters on a scale of 1 to 20.
HEPA vs HEPA type filter
Further Reading
Some links to interesting artices on HEPA filters.