Nominal or Absolute?

Absolute Rated
CFS filters in use

Absolute rated should mean the following:

A filter which has been tested via the modified OSU-F2 test(single pass) to show a filter which removes 99.98% of the challenge at 10 l /min flow from installation at the stated micron rating.

Any variation from this make a filter "non absolute", to most people, but filters are still promoted as absolute outside these guidelines..

The above is a Beta 5000 rated filter but you need to read the small print on competitors filters.

Some companies do not state at what stage the filter is tested. A filter where the removal is measured when it is 1/2 blocked means it was not offering the same removal when it was installed.

Some companies try to call 99% efficient "Absolute". This is far from absolute rated and when we are dealing with thousands of particles per milliliter, a move from 99.98% to 99% means thousands or millions of particles that would have been stopped may now pass through.

Due to the mechanisms of filtration which include Direct Interception, Inertial impaction, Brownian Motion, and Gravity if you increase the flow or stop start the flow this has to affect the removal efficiency, this must be taken into account.

Microbially rated and Particulate Rated, know the difference

Be aware that an absolute rated filter at say 0.2 will not stop everything at 0.2 micron! Yes this is true and a fact. If you have an absolute rated 0.2 micron filter in line with our definition above it may stop particles at 0.2 but please, please don't expect it to stop bacteria such as brevundimonus diminuta for this you must have a MEMBRANE filter such as PES(polyethersulphone) which is validated in line with HIMA guidelines (Health Industry Manufacturers Association) and rated at 0.2 micron. Only a membrane filter can stop bacteria with any real certainty.

There is a big difference between the two filter types and a big difference in the pre filtration required, getting this wrong could cost lives, let CFS help you and provide the knowledge and experience.

Nominally Rated Filters

If you are looking to buy a nominally rated filter its "Nominal Rating" means absolutely nothing without qualification. Yes this is true and a practice often exploited by the less scrupulous filtration sellers.

A customer may ask for a 1 micron nominal filter, another asks for a 20 micron nominal filter and a third asks for a 50 micron nominal filter and they are all supplied with the same filter from the same box marked as described by the less honest filter sales companies but have they done wrong? In essence no, and this is very common.  A nominal efficiency means that a filter will nominally remove a certain percentage at a given micron rating. A single filter could be 20% efficient at 1 micron, 50% efficient at 20 micron and 80% efficient at 50 icon but the same filter could be sold as a 1, 20 or 50 micron filter and this happens a lot. A law is not broken but I am sure customers would be unhappy if they knew this practice occurred. Would you be happy with a 1 micron filter which is closer a 100 micron filter? The solution... call CFS and get 100% total honesty.

The CFS the Graver Technologies nominally rated filters are clearly stated as nominal and also have their absolute rate stated.

The Liquapure range are Absolute rated or nominally rated at 90% or 80%.

Don't get caught buying a nominally rated filter elsewhere that has a micron rating which means absolutely nothing. CFS can offer the solution, we buy direct from manufacturers not bulk importers and we test filters ourselves, where required, in our laboratory to ensure that what we sell we have confidence in.