Airolite Company

Allegheny Power

Appalachian Power Corp.

Armco Steel

American Electric Power

American Municipal Power

Ames

A.E.C. Stacks

August Environmental

Ashland Chemical Company

Ashland Oil Company

American Boiler & Chimney Co.

B.F. Goodrich Corporation

Bechtel Power Corp.

Belco Technology Corp.

Bachmann Industries

Cabot Corporation

Combustion Engineering

Commonwealth Dynamics, Inc.

Controlled Demolition, Inc

Chapman Corp.

Cyanamid

Dick Corporation

Eichleay Corp.

E.I. DuPont Denemours

Elkem Metals Co.

F.L. Smidth & Company

GE Plastics

GE Environmental Systems, Inc.

Glitsch Package Plants

Gibraltar Chimney

Gilbert Commonwealth & Assoc.

Globe Metallurgical

Helmick Corporation.

Industrial Environmental Systems

Indiana & Michigan Electric Co.

Industrial Contractors

International Chimney Corp.

International Steel Services, Inc.

Kvaerner Songer Corp.

Kentucky Power

Legge Associates, Inc.

L.B. Foster

Monongahela Power Co.

Northwest Pipe

Ohio Edison Company

Oakpark Chimney

P.P.G. Industries, Inc.

Pioneer Pipe

Pullman Power

Pittsburgh Processing Corp.

Quaker State Refining Corp.

Roberts & Schaeffer Co.

SES, LLC

The Frederick Parker Group .

The Thompson-Starrett Co.

Trimble Engineers & Constructors

Union Carbide Corp.

United Constructors Co.

VSL Corporation

Whiting-Turner

Warren Environmental Corp.

Willis & Paul Group

Witco Corporation