The Truth About HEPA

Introduction:
There are a number of misconceptions about vacuum cleaner filtration in the cleaning industry. This article is meant to clarify the details about HEPA filtration.

History:
The original HEPA filter was designed in the 1940s and was used in the Manhattan Project to prevent the spread of airborne radioactive contaminants. It was commercialized in the 1950s, and the original term became a registered trademark and a generic term for highly efficient filters. Over the decades filters have evolved to satisfy the higher and higher demands for air quality in various high technology industries, such as aerospace, pharmaceutical processing, hospitals, health care, nuclear fuels, nuclear power, and electronic micro circuitry (computer chips).
Today, a HEPA filter rating is applicable to any highly efficient air filter that can attain the same filter efficiency performance standards as a minimum and is equivalent to the more recent NIOSH N100 rating for respirator filters. The United States Department of Energy (DOE) has specific requirements for HEPA filters in DOE regulated applications. Products that claim to be "HEPA-type", "HEPA-like", or "99% HEPA" do not satisfy these requirements and may not have been tested in independent laboratories.

What Does HEPA Mean?
HEPA filter stands for “High Efficiency Particulate air filter”. This filter is for filtering out particles contained in an airstream, at high efficiencies.

My upright vacuum is HEPA, can I pick up Asbestos?
No. There are different ways in which the term HEPA is used in the industry. HEPA Like, HEPA Type, True HEPA are just a few of them. A True HEPA for hazardous vacuum will have the following characteristics:

1. An isolated HEPA filter (Separate to the actual vacuum chamber)
2. Tested by an independent laboratory to specific standards
3. A certificate stating the standard used to test the HEPA filter/Vacuum (i.e. DOP)

Terms like "HEPA-type", "HEPA-like", or "99% HEPA" are generally marketing ploys to make consumers think they are getting true HEPA filtration.

What is a Particle?
A particle can be anything from a smoke particle to a grain of sand to a rock. It makes intuitive sense that it is harder to filter particles that are smaller in size. Keep in mind that not only does the size of the particle matter, but so does its velocity. A fast moving particle of a given size is harder to filter than the same particle at a lower speed. When filtering particles in the sub-micron range (less than 1 micron) it is not only the size of the particle that matters but also its shape and mass. In particular, particles at 0.3 microns have a lot of penetrating power.

What is a Micron?
A micron is a metric unit of measure which is one millionth of a meter. A meter is roughly 39.5 inches. For comparison, the average diameter of a human hair is 100 microns and the smallest particle the human eye can discern is 10 microns. It is important to know that the human upper respiratory tract is only capable of stopping particles that are 10 microns in size and larger. Particles smaller than 10 microns are considered 100% reparable meaning they escape the body's defense mechanisms.

What is Test Dust?
A test dust is a dust containing particles of a known size and distribution. One of the most common test materials is DOP (Dispersed oil particulate) smoke. Another common one is sodium chloride test dust.

What Do the Tests Measure?
Normally, overall filter efficiency is measured against the full distribution of particles in the test dust. If 100 milligrams of dust goes in and 0.1 milligrams comes out, the efficiency is 99.9%. If required, it is also possible (by a particle counting and sizing method) to establish the efficiency at a particular particle size. It is important to know that the filter test takes only a few minutes and the volume of test dust is very small. The test measures the efficiency during the test and does not predict how the filter will perform in actual use. Thus it does not test how long the filter will last before:

1. it clogs up and lets no air pass
2. it clogs up and particle pass through
3. it clogs up and air leaks past it

It is for this reason that careful design considerations are necessary to have a HEPA vacuum which is an efficient product and not just a product with an efficient filter.

Are HEPAFlo bags HEPA for hazardous?
No. HEPAFlo bags when used in combination with a Permatex/Microtex filter will give you a filtration of .3 microns at 99.97% efficiency. This meets the filtration portion of the HEPA standard, but the filter is not isolated. As indicated above, a true HEPA for hazardous vacuum has an isolated HEPA filter.
HEPAFlo bags are meant to improve overall indoor air quality in any facility by providing filtration that is equivalent to HEPA filtration without the added cost.

How Efficient Are NaceCare HEPA Vacuums?
The HZ range of vacuums offer HEPA filtration that is 99.99% efficient, or better according to the test standard used. These machines also offer 100% filtration to 0.5 microns, 99.97% filtration to 0.3 microns and 99.95% filtration to 0.1 microns. These results are for the complete vacuum cleaner and not just the filter. Hence the complete product has the above efficiencies - not just the HEPA filter itself.
After each machine is tested and approved, it is supplied with a test certificate indicating the test results for that particular machine. This means that the HEPA filter within the machine is being tested at the maximum air volume the machine can generate. The testing procedure for NaceCare machines is as follows.

1. A testing apparatus produces a sodium chloride particle cloud which is drawn through the filter by the machines motors.
2. Upstream and downstream particle levels are then measured using a photometer with sensitivity better than 5 nanograms per cubic meter. The equipment can measure penetration to 0.00005% at airflow of 1,700 cubic meters per hour.
3. The upstream and downstream values are compared to achieve filtration efficiency.
   This test is sometimes called the Sodium Flame test.

In addition, when a HEPA filter is mounted in a vacuum cleaner, it should be inaccessible to the user. This means they are unable to touch or manipulate the filter as doing so could damage it and render it useless.
 
 
 Sources:
Wikipedia - http://en.wikipedia.org/wiki/HEPA#Vacuum_cleaners
NaceCare Solutions – http://nacecaresolutions.com
Numatic International – http://numatic.co.uk