The Carl Moyer Program Off-Road Retrofit Exemptions

This page was last reviewed October 17, 2011


Retrofit manufacturers have provided ARB with exemption letters that identify retrofits that are not compatible with specific pieces of equipment. The exemptions are only valid for the retrofit and the equipment models identified in the letter. This page also lists exemptions that have been subsequently revoked by the retrofit manufacturer.

For those pieces of equipment that have a retrofit exemption listed, there may be other verified retrofits available for that equipment. Available retrofits can be found in the verification database

HUSS’s FS-MK filter system

Exemptions for the following equipment:

  • Caterpillar C13 slipform concrete paver
  • Caterpillar 3406 driver over truck unloader
  • Caterpillar 627 wheel tractor scraper
    • HUSS exemption revoked May 5, 2008 for Tier 3 or cleaner Caterpillar C18 and smaller engines. Physical installations on C18 engines will be available starting July 1, 2008.
  • Caterpillar 637 wheel tractor scraper
    • HUSS exemption revoked May 5, 2008 for Tier 3 or cleaner Caterpillar C18 and smaller engines.   Physical installations on C18 engines will be available starting July 1, 2008.
  • Caterpillar 651 wheel tractor scraper
  • Caterpillar 657 wheel tractor scraper
    • HUSS exemption revoked May 5, 2008 for Tier 3 or cleaner Caterpillar C18 and smaller engines.   Physical installations on C18 engines will be available starting July 1, 2008.

Caterpillar's Diesel Particulate Filter

Exemptions for the following equipment:


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