B.C. Air Quality

Diesel School Bus Retrofit Program

Project Objectives

Minister Penner with Diesel School BusThe B.C. Air Action Plan calls for making heavy-duty vehicles cleaner. "Clean up school buses" falls under Action #7 in the plan.

The objective of the Diesel School Bus Retrofit Program is to reduce emissions of diesel particulate matter (PM) from school-district-owned school buses. This will be done by applying emission-reduction devices to all eligible school-district-owned school buses, where appropriate.

For details on who is taking part, see Progress by School District.

The intent is to retrofit all school-district-owned diesel buses with an emission-reduction device if one is not already present. Two classes of devices will be considered for each bus:

  • exhaust retrofit devices — either a diesel-oxidation-catalyst (DOC) or flow-through filter (FTF); and
  • an engine retrofit — called a closed-crankcase ventilation (CCV).

The type of retrofit device(s) for a particular bus will be determined based on three key criteria:

  • the potential to reduce exposure of the bus occupants to particulate matter (PM);
  • attaining the largest emissions reductions possible for the service lifetime of the bus; and
  • the compatibility between the retrofit device and the bus engine.


Levels of outdoor pollutants generated from fossil fuel combustion are a public health issue in B.C. and Canada. Studies by Health Canada and community-health departments and agencies have shown a direct link between vehicle emissions and significant cardiac and respiratory health effects.

These studies have concluded that poor air quality and smog — caused in part by vehicle exhaust — are resulting in increased hospital admissions, respiratory illnesses such as asthma, and premature deaths, particularly in urban areas. Groups at risk include the elderly, children, people with heart and lung diseases and those with diabetes. Children are especially vulnerable to air pollution because they have growing and developing bodies and breathe in more air per pound of body weight than adults.

The exhaust from diesel-powered vehicles contains a variety of hazardous gases and particulate contaminants, including carbon monoxide, nitrogen dioxide, volatile organic compounds, sulphur dioxide, and fine particulate matter (especially the smaller particulate matter, called PM2.5). Diesel exhaust is classified as a known or probable human carcinogen by various governmental organizations such as the World Health Organization, and the United States Environmental Protection Agency.

Depending on the type and age of the vehicle, bus emissions may make their way into the bus cabin. The pollution comes from two sources: the tailpipe and the engine crankcase. Even though children may spend only a small portion of their day on buses, the high exposures they receive inside the bus can add considerably to their daily and annual exposures.

Previously, 550 school buses were retrofitted with diesel-oxidation-catalyst devices and/or closed-crankcase-ventilation systems in a voluntary program conducted by Environment Canada. It was estimated that the PM2.5 emissions were reduced by about 40% from these buses, for a reduction of 1.03 tonnes. This is equivalent to eliminating the PM2.5 emissions from approximately 17,000 average cars.

The budget for completing the retrofit of all school-district-owned buses is $1.2 million over three fiscal years.

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