What is a HEPA filter?
A filter is a device that traps and blocks small particles from going back into the air. A HEPA filter traps and blocks very small particles from getting back into the air. A certified HEPA filter is required and tested to trap particles as small as .3 microns with 99.97 % efficiency. One micron is 1/1,000,000 of a meter. A 0.3-micron particle is 300 times smaller than a human hair and 30 to 50 times smaller than the human eye can see.
HEPA stands for High Efficiency Particulate Air, and a true HEPA filter is widely regarded as the ultimate filter. In World War II the Atomic Energy Commission needed a filter to protect researches from radioactive dust particles that might present a health hazard to them. The HEPA filter was born. It traps particles as tiny as .3 microns with an efficiency rating of 99.97%. To give you an idea of the size of a micron, it takes 25,400 microns to equal 1 inch (2.54 cm). Conversely, 4/100,000ths of an inch equals one micron. In metric terms, a single micron is 1 millionth of a meter. A particle of 10 microns is invisible to the naked eye. Pollen ranges between 5-100 microns. Human hair between 70-100 microns. The rating for a HEPA filter is based on capturing nearly all microns .3 in size, verses .1 or even .001 because .3 microns are the hardest size to trap and the optimal size for passing into the human respiratory system. Therefore the .3 micron efficiency rating sets the highest sta
Start with what is the filter in a vacuum cleaner? A filter is a device that traps and blocks small particles from going back into the air. A HEPA filter traps and blocks very small particles from getting back into the air. A certified HEPA filter is required and tested to trap particles as small as .3 microns with 99.97 % efficiency.
Instead let us try folding the paper back and forth so that we can present a very large surface area to the airflow and thus the HEPA made this way would be efficient. This is how real-world HEPA filters are made in real HEPA systems. Some have as much as 40 square feet of the filter material folded into the HEPA section. As a side note the material from which HEPA is constructed is either fiber or paper-like on one hand or a polymer on the other. HEPA material does not look like a screen or a colander. Instead it looks like a very thin bail of fibers. Thus the air has to find a route through this maze of fibers. There are three ways the HEPA filter stops particulates. First and the easiest to understand is that a particle runs into a fiber and sticks. Secondly, the particle gets within one diameter of a fiber of the HEPA filter and while it tries to “skid by” the fiber it is gets stuck on the fiber. Third, as a very small, about 0.1 micron, particle moves in the gas flow it dithers ab
What Is HEPA? Arguably the most misunderstood concept of a vacuum cleaner is that of HEPA. We could spend a large amount of time trying to provide a lot of information, but our intent is to give an overview and cut through the clutter to supply you with a useful guide to HEPA filtration. During WWII, scientists developing the atomic bomb needed to devise a means of filtering small, not able to be seen particles. Out of this desire the HEPA standard was developed. HEPA is an acronym for High Efficiency Particulate Air. The HEPA standard demands that 99.97% of all particles (.3 microns or larger) must be captured by the filter media. That is a very exact standard. Lets also be clear on something. You and I are unable to see anything that is .3 microns in size without a microscope. For most people without respiratory issues, this is not an issue. But for people with allergies or respiratory problems this can be at the least, irritating, and at worst, life threatening. We are going to addr
