One of Nilfisk's biggest focus is filtration: What does HEPA stand for?
High Efficiency Particulate Air. Nilfisk was the first company to put a HEPA filter on a vacuum. The HEPA filter was developed originally as breathing filters during the Manhattan project in early 1940s to capture radioactive particles to protect the US soldiers and atomic scientists.
Most household pollutants are invisible. The heavier ones are pulled to the ground by the force of gravity, but lighter gases and particles remain airborne. Most of these airborne particles are invisible to the human eye. HEPA filters are the only way to trap contaminants like pollen, tobacco smoke and viruses.
HEPA filiter is made up of glass fibre paper and the filtration rate can be from 95% to 99.999%, concentrating on the most penetrating particle size, which is 0.3 micron (1 micron is 1 thousandth of a millimitre). A human hair is approximately 300 microns, Dust mites approximately 400 microns.
HEPA 14 is the highest grade filter on the market and captures 99.95% of all particles 0.3 micron or bigger.
What is just as important is how much air bypasses the filter - HEPA tight means that all seals are tight, letting nothing pass by the filter. HEPA filters are graded as H10, H11, H12, H13 and H14.
The following table shows the HEPA grade filtration class and the filtration efficiency of each HEPA filter.