San Francisco Bay Area
Air Quality Status
Sunday, 8/25
No Alert
Data and Records
Since the start of the Spare the Air program in 1991, the Air District has kept records for the number of alerts issued each year.
Particulate Matter Historical Data
There are different sizes of particulate matter, or PM, with the smaller, fine particles posing a greater risk to public health. PM 2.5 refers to particulates that are 2.5 microns or smaller, about 1/28 the size of a human hair.
The PM 2.5 standard was introduced by the federal government in 2000 and strengthened in 2006. The national 24-hour standard for PM 2.5 is 35 micrograms per cubic meter.
The tables below list the number of Winter Spare the Air days issued for the Bay Area for each November-December Winter Spare the Air season or calendar year, as well as the number of days on which PM concentrations exceeded the state and federal health-based air quality standards.
By Season (November - February)
|
Winter Spare the Air Season
|
Winter Spare the Air Alerts
|
National 24 Hour PM 10 Excess Days
|
CA 24 Hour PM 10 Excess Days
|
National 24 Hour PM 2 5 Excess Days
|
|---|---|---|---|---|
| 2018-2019 | 4 | 0 | 0 | 1 |
| 2017-2018 | 19 | 0 | 0 | 7 |
| 2016-2017 | 7 | 0 | 0 | 0 |
| 2015-2016 | 1 | 0 | 0 | 0 |
| 2014-2015 | 23 | 0 | 0 | 6 |
| 2013-2014 | 30 | 0 | 7 | 15 |
| 2012-2013 | 10 | 0 | 1 | 1 |
| 2011-2012 | 15 | 0 | 4 | 11 |
| 2010-2011 | 4 | 0 | 0 | 1 |
| 2009-2010 | 7 | 0 | 2 | 9 |
| 2008-2009 | 11 | 0 | 0 | 13 |
| 2007-2008 | 6 | 0 | 3 | 7 |
| 2006-2007 | 30 | 0 | 6 | 20 |
By Year
|
Year
|
Winter Spare the Air Alerts
|
National 24 Hour PM 10 Excess Days
|
CA 24 Hour PM 10 Excess Days
|
National 24 Hour PM 2 5 Excess Days
|
|---|---|---|---|---|
| 2019 | 1 | 0 | 0 | 0 |
| 2018 | 3 | 0 | 0 | 2 |
| 2017 | 19 | 0 | 6 | 18 |
| 2016 | 5 | 0 | 0 | 0 |
| 2015 | 17 | 0 | 0 | 6 |
| 2014 | 13 | 0 | 2 | 3 |
| 2013 | 33 | 0 | 6 | 13 |
| 2012 | 5 | 0 | 1 | 3 |
| 2011 | 12 | 0 | 3 | 8 |
| 2010 | 6 | 0 | 2 | 6 |
| 2009 | 9 | 0 | 1 | 11 |
| 2008 | 6 | 0 | 5 | 12 |
| 2007 | 23 | 0 | 4 | 14 |
| 2006 | 12 | 0 | 15 | 10 |
| 2005 | 0 | 0 | 6 | 0 |
| 2004 | 0 | 0 | 7 | 1 |
| 2003 | 0 | 0 | 6 | 0 |
| 2002 | 1 | 0 | 9 | 7 |
| 2001 | 0 | 0 | 12 | 5 |
| 2000 | 0 | 0 | 7 | 1 |
| 1999 | 0 | 0 | 12 | N/A |
| 1998 | 0 | 0 | 5 | N/A |
| 1997 | 0 | 0 | 4 | N/A |
| 1996 | 0 | 0 | 3 | N/A |
| 1995 | 0 | 0 | 7 | N/A |
| 1994 | 3 | 0 | 9 | N/A |
| 1993 | 0 | 0 | 10 | N/A |
| 1992 | 1 | 0 | 18 | N/A |
| 1991 | 11 | 2 | 18 | N/A |
24-Hour PM Standards
- The national 24-hour air quality standard for PM 10 was set at 150 micrograms per cubic meter of PM 10 in the ambient air, averaged over 24 hours.
- The California 24-hour standard for PM 10 is set at 50 micrograms per cubic meter in the ambient air, averaged over 24 hours.
- The national 24-hour standard for PM 2.5 is set at 35 micrograms per cubic meter of PM 2.5 in the ambient air, averaged over 24 hours. (Prior to 2006, the standard was set at 65 micrograms per cubic meter.)
- The California 24-hour standard for PM 2.5 is currently in the process of being determined.
