Texas Air Control Board
           Austin                       Texas
                        Interoffice

To:  Permit Engineers and Regional Supervisors
From:  Jim Myers, P.E.     
Date:  April 23, 1980
Subject:  Interpretation of the Standard Exemption List

It is the purpose of the standard exemption list to define
equipment and processes which when considered individually are
insignificant sources of air contaminants.  Combinations of
such equipment or processes may constitute a significant
source of air contaminants and thus not be entitled to an
exemption.  It is, therefore, requested that the following
guidelines be used in the application of the list:

1.  Combinations of equipment and processes should be
    considered collectively in determining the significance of
    the emissions.
2.  If a combination of processes or equipment fits a standard
    exemption or a combination of standard exemptions and the
    emissions from the entire new facility do not exceed our
    25 TPY guideline, construction pursuant to the standard
    exemptions is in order.
3.  If, however, emissions from a combination of processes or
    equipment which would otherwise fit standard exemptions
    which will be located on a property will exceed the 25
    tons per year guideline, a permit is required prior to
    construction of any one of the processes or equipment
    involved.