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.

Though several factors, including weather conditions and disasters such as wildfires, may influence the number of Spare the Air and Winter Spare the Air alerts called within a given year, there has been an overall increase in alerts.

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.
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San Francisco Bay Area
Air Quality Status
Tuesday, 6/25
No Alert

5-Day Air Quality Forecast
Mon
Tue
Wed
Thu
Fri
Northern Zone
42
35
G
G
G
Coast and Central Bay
46
34
G
G
G
Eastern Zone
58
37
G
G
G
South Central Bay
47
35
G
G
G
Santa Clara Valley
54
36
G
G
G
Tuesday, June 25
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