Testing

Our gowns are developed to different test methods, and is explained below. Class 1 (Level 1 and Level 2 gowns are not waterproof they are water repellent and some people even avoid using the term water repellent and only use water resistant for level 1 and level 2. The truth is that the term water repellent is a little loosely used and there are degrees of repellency as you can see by the tests and specifications. BUT it does not mean waterproof.

To follow, I explain the differences in the tests and the standards. At the end, I have a link to a video that explains the proper testing procedure. 

AATCC 22 Repellency Spray Test

This test method is applicable to any textile fabric, which may or may not have been given a water-repellent finish. It measures the resistance of fabrics to wetting by water. It’s especially suitable for measuring the water-repellent efficacy of finishes applied to fabrics. Water sprayed against the taut surface of a test specimen under controlled conditions produces a wetted pattern whose size depends on the relative repellency of the fabric. Evaluation is accomplished by comparing the wetted pattern with pictures on a standard chart. The water residue and drops that remain on the fabric are compared to the chart 80 being very good, 90 being excellent and 100 as perfect. Our fabric tests come in at an 80. This is the most common repellency test used outside of what is being used for medical devices in the USA.

AATCC 42 Test (Used by U.S. AAMI Standard)

AATCC 42 is a water impact penetration test. In this case they use the same apparatus but are less focused on how easily the water runs off the fabric and more interested in seeing how much water penetrates the fabric. The difference is in how the fabrics are tested. The fabrics for both are developed and treated the same way with the same process. They are just looking for 2 different things.

NOTE: The angle of the fabric is very important in both tests so that the water deflects and/or runs off the fabric. If you test with a water faucet directly on horizontal fabric that has creases in it, it will not perform well in either test. Same with the seams. In the case of the AATCC 42 (For medical in the USA) They put an absorbent paper (that gets weighed before the test) underneath the fabric prior to testing the fabric and they weigh it again after the test. This tells them how much moisture makes it through the fabric. The level 1 spec says that it should only increase by .40 grams tested on the fabric and on the seam. So, they do expect some penetration. That is why level 1 and level 2 are considered minimum to low barrier protective fabrics. For Level 3 and 4 fabrics, they are basically waterproof and have a waterproof film or waterproof coating applied to the fabric in the critical zones. 

A fabric treated for one test would typically perform in the other test. The difference would be possibly the level of performance it would have if it was treated for one test verses the other. For example, a more open fabric may sill perform fairly well in the AATCC 22 and not so well in the impact test. And a very closed fabric may not perform as well in the AATCC 22 spray test if it does not have enough repellent or it is not a smooth fabric. Our fabric was developed for the AATCC 22 standard and fortunately, our fabric performed fairly well in both tests as developed. Initially we were boarder line to a little high on the fabric and seams on the AATCC 42 (US MEDICAL TEST) so we have been making some adjustments re-enforce by tightening the weave a little and adjusting the chemistry so we can pass the AAMI performance. The specification for a level 1 gown is less that .40 grams of water passing through. We were running between .35 to .60.