EPA Air · stack tests by state and year

Air-emissions stack tests in California, 2024

• 18,905Stack tests

A stack test measures what a source actually emits, at the stack, against the limit in its permit. Every stack test below was recorded against a source in California during 2024; one facility can appear more than once, because this is a record of what happened rather than a list of places.

Counties in California, 2024

• Kern County 7,524
• San Joaquin County 5,176
• Stanislaus County 3,977
• Fresno County 597
• Merced County 538
• Madera County 235
• Kings County 204
• Tulare County 195
• Los Angeles County 169
• San Bernardino County 90
• Monterey County 36
• Orange County 35
• Riverside County 31
• Ventura County 27
• Sacramento County 25
• San Diego County 15
• Placer County 12
• Undetermined County 10
• Santa Cruz County 5
• Humboldt County 3

California, other years

• 2026 979
• 2025 5,390
• 2023 7,676
• 2022 10,813
• 2021 17,676
• 2020 15,352
• 2019 6,897
• 2018 7,098
• 2017 8,621

Air-emissions stack tests recorded in California, 2024

Dates as filed by the agency that recorded the stack test. Figures from EPA’s ICIS-AIR download.