Particulates, alternatively referred to as particulate matter (PM), aerosols or fine particles, are tiny particles of solid or liquid suspended in a gas. They range in size from less than 10 nanometers to more than 100 micrometers in diameter. The notation PM10 is used to describe particles of 10 micrometers or less and PM2.5 represents particles less than 2.5 micrometres in aerodynamic diameter; other numeric values may also be used. This range of sizes represent scales from a gathering of a few molecules to the size where the particles no longer can be carried by the gas. Sources of particulate matter can be anthropogenic or natural.

Some aerosols occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels also generate aerosols. Averaged over the globe, anthropogenic aerosols—those made by human activities—currently account for about 10 percent of the total amount of aerosols in our atmosphere.

A PM10-efficient street sweeper is a street sweeper that is certified by the South Coast Air Quality Management District (SCAQMD) as meeting the testing and performance standards set forth in SCAQMD Rule 1186. All certified street sweepers must be operated and maintained in accordance with manufacturer’s specifications.


PM10-efficient street sweepers may be used for cleaning carryout and trackout on a public paved roadway from traffic leaving a construction site, an unpaved road or equipment area, or the handling of bulk materials. Using blower devices, or dry rotary brushes or brooms for removing carryout and trackout on a public road is prohibited.

PM10-efficient street sweepers are also used for routine street sweeping in urban areas. As of June 1, 2005, government agencies are required to purchase only PM10-efficient street sweepers. This requirement also applies to the contractors who provide street sweeping services to these agencies. There are no retrofit allowances under SCAQMD Rule 1186. Agencies conducting or contracting for routine street sweeping services must place into service at least one PM10-efficient street sweeper by June 1, 2008