The Regional Air Pollution Control Agency

Diesel Retro-Fit Project

Diesel Oxidation Catalyst

In July 2004, RAPCA teamed up with the Montgomery County Board of Metal Retardation and Developmental Disabilities (MRDD) and installed diesel oxidation catalysts (DOC) on 38 MRDD school buses. This project is part of USEPA's Clean School Bus USA program that is designed to reduce both children's exposure to diesel exhaust and the amount of air pollution created by diesel school buses.

The term "retro-fit" refers to replacing or modifying components of an existing exhaust system with a pollution control device to reduce exhaust emissions. In this project mufflers were simply replaced with a DOCs.

What does a Diesel Oxidation Catalyst Do?

Oxidizes CO and HC to CO₂ and H₂O
Achieves CO and HC emission reductions greater than 90%
Achieves particulate matter (PM) reduction between 20-50%

Maintenance and Application Requirements

Can work with high sulfur fuel (up to 500 ppm)
Benefits from low sulfur fuel
No maintenance
Easy installation

Project Overview

Project was funded by EPA's Clean School Bus USA Program.
38 buses installed with diesel oxidation catalyst (DOC)
Installation time per bus approximately 1 hour
Project cost was $36,740 ($967/bus including installation)
Project Pictures
News Release

Note: Cost of DOC's are continuing to drop

Clean School Bus USA

Clean School Bus USA brings together partners from business, education, transportation, and public health organizations to work toward these goals:

Encouraging policies and practices to eliminate unnecessary public school bus idling.
Upgrading ("retrofitting") buses that will remain in the fleet with better emission control technologies and/or fueling them with cleaner fuels.
Replacing the oldest buses in the fleet with new, less polluting buses.

RAPCA is encouraging local school bus fleets to participate in the Clean School Bus program.

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