Rule 409  Exemptions to Rule 408.  The Air Pollution Control
          Officer may exempt from the provisions of Rule 408 any
          of the following facilities or modifications, or
          portions thereof, with respect to attainment

     A.   Portable facilities being relocated which have received
          Permits to Operate after January 1, 1981, and temporary
          sources of emissions if:

          1.   Emissions from the facility would not exceed
               emissions limitations provided in these Rules and
               Regulations and would not cause or contribute to a
               violation of a national ambient air quality
               standard; and

          2.   Such operation would impact no Class I area and no
               area where an applicable increment is known to be
               violated; and

          3.   Notice is given to the Air Pollution Control
               Officer at least 90 days prior to a relocation
               identifying the proposed new location and the
               probable duration of operation at such location.

     B.   Modification of a source for the sole purpose of
          converting from the use of petroleum products, natural
          gas, or both, by reason of a natural gas curtailment
          plan in effect pursuant to the Federal Power Act or the
          Federal Energy Supply, and Environmental Coordination
          Act of  1974 (or any superseding legislation).  An
          exemption for such modification shall not apply for
          more than five (5) years after the effective day of
          such plan.

     C.   Any modification which causes no net increase in the
          quantity of emissions from a facility, or any facility
          which causes no net increase in the quantity of
          emission within a District zone.  Emission offset
          eligibility shall be determined through the provisions
          of Rule 411.  No exemption shall be allowed if the
          facility or modification would impact a nonattainment
          area or an attainment pollutant increment violation
          area for such pollutant.

     D.   Sources of fugitive dust.

     E.   Any facility or modification which is not a major
          facility or major modification except any which would
          have the potential to emit an increase of emissions in
          excess of:

          1.   5.0 tons per year of lead;

          2.   0.02 tons per year of asbestos;

          3.   0.001 tons per year of beryllium;

          4.   0.3 tons per year of mercury;

          5.   3.0 tons per year of vinyl chloride;

          6.   3.0 tons per year of fluorides;

          7.   7.0 tons per year of sulfuric acid;

          8.   10.0 tons per year of hydrogen sulfide;

          9.   10.0 tons per year of total reduced sulfur.

     F.   Any source of carbon monoxide which the Air Pollution
          Control Officer determines would not cause a violation
          of any national ambient air quality standard for such
          pollutant at the point of maximum ground level impact.