My industry, industrial cleaning, is going through a transition—from the aftermath of the CFC phaseout to something else.

The CFC phaseout left users with few and often unsatisfactory options. Most replaced CFC solvents with an aqueous cleaning system. Certainly that’s true in the plating industries, where process steps after cleaning are often completed in a water solution, eliminating the need for drying.

A decade and more later, those aqueous systems show age and demonstrate the inherent flaws in aqueous systems.1

Many users want something newer, or better—the rapid, low-energy, small floor space, high-quality cleaning formerly provided by CFC solvents. They are interested in replacement systems for those purchased in the last decade.

They are interested in new, lower-cost technology and seek the possibility of non-CFC solvents whose use makes sense with: (1) few environmental concerns, (2) reliable and repeatable performance, and (3) reduced operating and investment cost.

This column has been one site where these options have been discussed for the last year. Another site for discussion and evaluation of new options can be a trade show. In the first week of May in Louisville, Ky., we had one at PCX, an event completely dedicated to cleaning technology.


PCX—or Process Cleaning Expo—is a new show. It was intended to replicate the successful experience of the Precision Cleaning/CleanTech shows from the 1990s by providing: (1) a display of equipment, (2) some semi-commercial educational presentations, and (3) other presentations by regulators.

An unusual aspect of PCX was the presence of a purely scientific “track” focusing on removal of particles from surfaces.

This column will briefly summarize what this author saw, heard, and learned.

n-Propyl Bromide (n-PB)

By far, Margaret Sheppard was the most awaited speaker. She is teamleader for the USEPA’s Significant New Alternatives Policy (SNAP) Program. After more than a decade, Margaret’s team “validated” use of n-PB as a replacement for CFC cleaning solvents in 20072, and not an acceptable aerosol cleaning solvent in 2008.3

But the December 2009 decision by the state of California’s OSHA group to lower the required (not recommended) exposure limit to 5 ppm (after nearly requiring a value of 1 ppm) heightened expectation that might bring about a similar pronouncement by USEPA.

That was not to be. What was to be was of no lesser concern. It was that: There is a draft report on carcinogenicity available from National Toxicology Program (NTP).4 Its brief and significant finding is: “...Conclusion: clear evidence of carcinogenic action due to n-PB in both rats and mice....” There was also evidence of non-carcinogenicity found.

NTP’s finding is in the stage between peer review and publication. And it will not be the last word on the issue of carcinogenicity.

But NTP’s finding combined with the previous finding between n-PB and reproductive toxicity, which spawned the action by CAL OSHA makes permanent conversion to n-PB as a cleaning solvent no better than a short-term palliative. For some, that may be OK.

EPA’s charter is not to set required exposure limits—that’s one reason why the 2007 SNAP decision contained a recommended and not a required exposure limit. Exposure limits are to be set by the National Institute for Occupational Safety and Health (NIOSH). They have, after years of delay, accepted the challenge of developing a required exposure limit. The discussion may center around whether or not the value will contain two or a single digit of ppm.

Today, most n-PB is—and has been—imported from China. One can buy it, without technical support, from suppliers who advertise on the Internet for prices just above $1/lb. Specifications are excellent.

Some Good News

The 100 or so paying attendees seemed active, interested, and young. The latter is a characteristic badly needed in this industry.

The other presentation most populated seemed to be that covering cleaning fundamentals. Users we spoke with wanted to know “how and why things work.”

And no doubt, business was done at PCX. Some users and suppliers were actively courting one another.

Equipment on Parade

About 25 of the 30 show booths were populated with the names of U.S. suppliers familiar to readers of advertising in this magazine. An additional five or so were from Germany. They attended, at least, to gauge the U.S. market.

Two products of interest to this author were:

A low pressure (75 psig) air-driven system into which liquid CO2 is injected to for dry ice particles on expansion. This is a low-energy device5 for stripping coatings and barnacles— without environmental concern.

A high-speed turbine blower providing high-velocity air for drying of parts—without use of an air compressor. What was unique was the apparent sound reduction capability of the enclosure into which the turbine is housed, without a flow reduction. However, selling prices were not attractive, at least not to this author.

There will be new high-price “designer” solvents produced with two aims: (1) new functionality in a fluorinated solvent, and (2) lower Global Warming Potential (GWP).

There will be available in ~2011: fluoroketones, hydrofluoroolefins (HFOs), and unsaturated HFCs. Most will be VOC exempt. A pound of these new solvents and a carton of cigarettes will cost the same.

2011 (Hello, Columbus)

Many expect that there will be another show next year, co-located with a general manufacturing trade show and sited in Columbus, Ohio. Management of PCX logistics was excellent and of high quality.

Need For Good Options

The renewed concern about n-PB will certainly raise interest in the flammable trans-1,2,-dichloroethylene or the probably carcinogenic trichloroethylene.

More significantly, today’s situation speaks to the need for better options: (1) aqueous technology, which is less “cumbersome” and can be done at room temperature, and (2) solvent technology which doesn’t threaten.
These options need to be accompanied by clear, fair, accurate communications. Users are tired of the feel-good—but fundamentally meaningless—terminology of “environmentally friendly,” “green,” and “low-cost” technology. Nearly every good displayed at PCX carried one or more of these labels.

Author’s Impressions

Compared to the cleaning shows of the 1990s, PCX was a small show. But in terms of content, it was anything but small. And that content is a necessary factor for technology growth and innovation in parts cleaning.
Today, when corporate travel to educational events is limited because of business conditions, PCX was a valuable stepping stone to renewed vitality.

  1. All cleaning systems, as well as authors, have flaws. The comment is descriptive, not derogatory.
  2. EPA issued a final rule in May 2007 finding n-PB acceptable for solvent cleaning (vapor degreasing, enclosed equipment w/conveyors). See: May 30, 2007; 72 FR 30142.
  3. EPA has proposed to find n-PB: (1) unacceptable as an aerosol solvent or carrier solvent for adhesives, and(2) acceptable subject to use conditions for use as carrier solvent in coatings. See May 30, 2007; 72 FR 30168. EPA is in process of considering responses to public comment and drafting a final rule for aerosols and adhesives. A final rule expected later in 2010.
  4. It can be downloaded from
  5. The first two figures are courtesy of Gardner Publications. The third figure is courtesy of mycon GmbH(








John Durkee is the author of the book Management of Industrial Cleaning Technology and Processes, published by Elsevier (ISBN 0-0804-48887). He is an independent consultant specializing in metal and critical cleaning. You can contact him at PO Box 847, Hunt, TX 78024 or 122 Ridge Road West, Hunt, TX 78024; 830-238-7610; Fax 612-677-3170; or