ASTM D3574 - Test G - Testing Apparatus

This paper is intended as a comparison of the "ONIX" instrument described in Test G (Air Flow Test of ASTM Standard D3574) with the Frazier Differential Pressure Air Permeability Instrument (ASTM D737)

The two instruments are designed to do substantially the same test but were intended to test different types of materials.

Over the years the Frazier Differential Pressure Air Permeability Tester which was originally designed by the National Bureau of Standards (now NIST) to be used on thin textile like materials, has increasingly been used to determine the air permeability of many diverse materials including materials such as foam, that are relatively thick in depth by means of ingenious adaptations to its clamping arrangement.

The major differences between the two instruments is that the Frazier Instrument measures air flow with a series of calibrated venturi nozzles that have an inherently stable calibration and have a very high precision and repeatability. The Frazier Instrument calculations also read out permeability as cubic feet of air flow per minute per square foot of test area for simplicity of use in further calculations. Also it can be easily
configured to read in metric. The Frazier Tester also tests to much lower airflows than the ONIX.

The ONIX Air flow apparatus of ASTM D-3574 test G utilized a series of air flow gages that are inherently less accurate and do not have an adequate means of checking their calibration under everyday use conditions. (See section 63.4 of D3574.) It is an outdated technology. The ONIX tester is also no longer produced or supported.

Note 21 of D-3574 even notes that test Method D737 (The Frazier Instrument) can be substituted for D 3574 Test G.

The Frazier Instruments are widely available and recognized as the standard instrument in air permeability measurement. The Frazier Permeability Tester is widely used throughout the foam industry using both the D737 and D 3574 methods. For testing foam samples The D737 method implements The Universal Specimen Holder for testing samples up to 6" thick while the D3574 method implements the D3574 Specimen Holder.

Throughout the foam industry, The Frazier Air Permeability Instrument is used by industry leaders: BASF, Foamex, Tyco, General Electric, General Motors, Toyota, Lear Corporation, and DuPont. [Frazier Customers]

In addition an electronic variation of the original Frazier Instrument is now available from the Frazier Precision Instrument Co. of Hagerstown, Maryland. This instrument utilizes electronic sensors and a custom computer program to calculate permeability and input the results directly to the user’s computer.


Previous names of the ONIX unit are: AMSCOR Foam Tester, AMSCOR foam porosity instrument, Amscor Dow, onyx, Thermo Onix, Thermo, Onix Process Analysis, Onix systems.