"Although mite fecal particles are 10 to 40 µm [microns] in diameter, a significant proportion of cat allergen is associated with particles less than 10 µm in diameter. Because of the size of particles carrying Fel d 1 and the quantity of this allergen in dust samples, cat allergen was used to provide a more rigorous test of the fabric's ability to block passage of allergens."

Another result from this study that many have focused on had to do with something called mean pore size. Pore size is a reference to the openings where woven fibers intersect in a piece of material. Here's what was published:

"Dust mite allergens (Der f 1 and Der p 1) were blocked below detectable limits by fabrics of less than 10 µm in pore size. Fabrics with an average pore size of 6 µm or less blocked cat allergen (Fel d 1)."

"For woven fabrics, the key factor in blocking allergens is pore size. Our results show that a woven fabric with an average pore size of 6 µm or less will block common indoor allergens below detectable limits."

"Our current judgement is that fabrics of 2 µm to less than 10 µm in pore size will effectively block passage of all dust mite allergen and would be suitable for use on pillow cases and mattresses."

Mean pore size is best determined by using a capillary flow test. PMI (Porous Materials, Inc.) has performed capillary flow tests for many textile manufacturers and is a leading authority in this field of study. You can learn more about how those tests are performed by visiting PMI's web site. The U.Va. study did not develop a test method or protocol for determining mean pore size. Often the reporting of pore size is done either by the manufacturer of the fabric (like we do) or by the retailer selling the finished goods. In addition to the results reported by the manufacturers of fabrics used in our encasings, we have employed PMI to test samples we sent them. The results of that testing are posted here.

It's important to remember that there is no requirement to use a company like PMI when reporting mean pore size. Anyone with a microscope and a lens with a built-in micrometer (used to measure things in terms of microns) can give an opinion concerning the mean pore size of a woven fabric by simple observation. And this leaves open a number of questions. For example, how many samples are needed to come up with a "mean"? When using a simple observation technique, that's left up to the one doing the reporting. Additionally, the pore size of fabric will not remain completely uniform simply due to the fact that it is woven material. That means some pores are larger than others. So that leaves open the possibility of taking samples until the desired result is reached - be that good or bad. Consequently, it becomes important to find out how a reported mean pore size was determined and to request a copy of the independent test results.

Up until now, National Allergy has not relied exclusively on the reporting of pore size to determine product efficacy but rather has chosen to rely only on tests that IBT Reference Lab performs to establish how good a barrier an encasing fabric will be. The primary test employs the exact same protocol developed in the U.Va. study discussed above whereby an attempt is made to vacuum cat and dust mite allergen through the fabric. Random samples of fabric are sent to IBT for these tests, and we rely on the results to establish the barrier efficiency of the fabrics we use. Recently, IBT has begun using this same test on the seams as well. From time to time, we also ask IBT to run a "use simulation test" that attempts to determine if dust mite allergen will pass through a fabric as a result of your movement in bed. As you can see, we really try to do our homework before making encasings for you! See the results of IBT independent testing in the chart below.

There is a notable push in the marketplace by companies and individuals who want doctors to insist on the much more subjective measurement of pore size as the main determinant of performance. We're glad to publish that information for all of our encasings to which it applies (waterproof encasings like BedCare Classic™ don't have "pores"), and you will find it in the product description for all of our woven fabric styles. We report what the fabric manufacturers tell us, but please be aware that these are still very subjective numbers because they are averages and anyone else taking the readings could come up with a different average. Independent IBT Lab test results are available for all our fabrics. Please see the chart above.