PAO-4 (Emery 3004)

EMERY 3004 was a trade name for 4cSt polyalphaolefin, CAS #68649-12-7. The Henkel Company originally manufactured Emery 3004 PAO which was used in the initial research performed by Dr. Hugh Carlon et al.

ATI carries 4 cSt polyalphaolefin, sold under the name PAO-4, in stock for the convenience of its customers. PAO-4 is sold in 1 or 5-gallon containers and may be shipped via UPS or Federal Express. The 5-gallon container has a built in pour spout to aid customers in transferring to smaller vessels or filling aerosol generators.

The US Army Surgeon General has approved 4cSt PAO as the official replacement liquid for Di (2-ethylhexyl) phthalate (DOP, DEHP), CAS #117-81-7. Please note that it is not up to the liquid manufacturer to approve it for a specific use. Most government agencies or departments do not approve anything.  For example, 4cSt PAO is not approved by the Department of Energy; however the Department of Energy accepts the use of PAO as a replacement for DOP.  A letter from Robert L. Sorensen of the U.S. Food and Drug Administration to the Director of Quality Assurance of Eli Lilly and Company states that based on submitted documentation, research work, and papers, the FDA concurs with the U.S. Military that 4cSt PAO is an acceptable replacement for DOP.

There have recently been rumors that 4cSt PAO manufactured at different sites are not suitable replacements for DOP/DEHP.

The following is an excerpt from the Food & Drug Administration’s Human Drug CGMP Notes

(Vol. 4, Number 4), December 1996.

“The original manufacturing site which produced the Emery 3004 (PAO) for the data submitted has changed since the study and Emery 3004 (PAO) is now manufactured at a different site. Discussions with the Army and the companies involved in the original studies indicate the product remains the same from the new site of manufacturing. CDER has also compared the original specifications and the new site specifications along with data from the Material Safety Data Sheets and agrees that there is no significant difference in the product from either site.

The Chemical Abstracts Service (CAS) number which identifies this product also remained as 68649-12-7.

Other reported alternatives used in the industry include DOS (Di (2-ethylhexyl) sebacate) and Ondina Oil. However, no manufacturer has yet submitted all the necessary data to evaluate these alternatives.”

As such, Emery 3004 PAO with the CAS number 68649-12-7 still remains an acceptable replacement for DOP.”

Contact for further information:

Michael J. Verdi, HFD-322

Phone: 301-594-0095


Other relevant developments that ATI feels its customers should be aware follow:

  1. Beginning in the mid-2000’s some manufacturers of 4cSt polyalphaolefin began using dual CAS#’s to define the product they were producing. 4cSt polyalphaolefin previously identified as CAS# 68649-12-7, began including CAS# 68037-01-4, even when supplied by the same manufacturer under the same product number. The explanation was that the “new” CAS#, 68037-01-4, more accurately defined the product than the older number.

ATI has performed comparison testing on aerosol characteristics relevant to both filter leakage and efficiency testing and found no material difference between the two CAS identified products. The aerosol particle size distribution produced, aerosol properties and photometric response were the same.

  1. The U.S. Army, in conjunction with some Government attorneys, has acquired patents on the use of this liquid to generate aerosols. The first patent number 5,059,349 was issued on 22 October 1991. This patent is very specific in nature and covers the use of PAO and its use as a liquid to generate a monodispersed aerosol in the ATI TDA-100 Aerosol Penetrometer that is used for measuring the efficiency of respirator filters. The second patent 5,059,352 was issued on the same date. This particular patent covers the liquid PAO and its use in a prototype aerosol penetrometer that is no longer used for performing aerosol filter testing. The third patent 5,076,965 was issued on 31 December 1991 and covers the use of PAO liquid as the substance in a TSI model 8110-filter tester. These three patents really have no application in the normal in-place filter certification work that is carried out worldwide in the pharmaceutical, electronic, and aerospace industries, although it is believed that one pharmaceutical company did pay the Army for a license agreement.