The Chevron El Segundo Refinery , California, has been a fixture of Southern California’s energy landscape since 1911. For more than a century it has refined crude oil into gasoline, jet fuel, diesel, and other petroleum products that power the region. Yet alongside its role as an energy hub, the refinery has also been the source of recurring community complaints about foul odors drifting into surrounding neighborhoods. From rotten egg smells linked to hydrogen sulfide to smoky plumes from flaring, these odor incidents have been part of the refinery’s history and remain a central issue for residents and regulators.
Why Refineries Produce Odors
Refineries are complex industrial systems that operate under high heat and pressure to transform crude oil into usable fuels. In this process, gases are separated, heated, treated, and stored before being sent to market. During routine operations or system upsets, some of these gases can escape into the air, producing noticeable smells. Common culprits include hydrogen sulfide, which smells like rotten eggs even at very low concentrations, mercaptans and other sulfur compounds, volatile organic compounds, and hydrocarbons released during maintenance or flaring. Even when emissions are below regulatory thresholds, human noses are sensitive enough to detect odors at levels far lower than those considered unsafe. This explains why odors can be strong and unpleasant even if air quality officials say pollutants are technically within limits.
Historical Timeline of Odor Complaints
The history of odors at Chevron El Segundo stretches back decades, but several incidents stand out as significant examples of how often and why these events occur.
October 2009: Chevron filed reports of flaring tied to maintenance on its Isomax hydrocracking unit. While flaring is designed as a safety measure, it often produces smoke and odors that drift into nearby neighborhoods, raising concerns about air quality.
January 22, 2013: A malfunction in Chevron’s sulfur treatment units triggered a wave of odor complaints across nearby Manhattan Beach and surrounding areas. Residents described the smells as strong and unpleasant, permeating homes and businesses.
January 31, 2021: Over 30 odor complaints were logged by residents in El Segundo, Manhattan Beach, and surrounding South Bay communities. Inspectors traced the source to a hydrogen sulfide release during petroleum naphtha transfer to a storage tank. Fenceline monitors recorded one-hour averages as high as 168.7 parts per billion of hydrogen sulfide, far above the level detectable by smell.
February 4, 2021: Following the January event, regulators issued a Notice of Violation against Chevron for causing a public nuisance under air quality rules. This marked one of the most formal enforcement actions tied directly to odors from the refinery.
August 2021: A compressor failure at the refinery led to a flare event visible in the night sky. Alongside flames and black smoke, residents reported strong odors that carried into nearby neighborhoods.
November 2022: A fire broke out at the refinery in the evening, requiring hours to contain. During the response, emergency flares were triggered, adding to visible emissions and odor complaints from surrounding communities.
May 2025: Chevron reported an unplanned flare event, which again produced visible smoke and odors, drawing resident complaints and regulatory filings.
October 3, 2025: A major fire and explosion in the Isomax 7 unit triggered multiple safety flares. The blast produced significant smoke and strong odors across El Segundo and beyond, leading to widespread concern and a renewed focus on refinery safety and emissions.
These incidents illustrate that odor events at Chevron El Segundo are not isolated anomalies but part of a recurring pattern tied to maintenance, equipment failures, power outages, and emergency flaring.
Community Impact and Concerns
For residents living near the refinery in El Segundo and neighboring South Bay cities, odors are more than just unpleasant smells. They create anxiety about air quality, health risks, and the transparency of refinery operations. The rotten egg smell of hydrogen sulfide, for instance, is detectable at extremely low concentrations but also associated with respiratory irritation and nausea at higher levels. Visible smoke from flares adds to the perception of danger, even if officials classify events as “controlled.”
Over time, odor events erode trust between the refinery and the community. Residents often feel that they are not adequately notified of planned flaring or maintenance that could cause odors. Complaints that odors are dismissed as harmless nuisance smells add to frustration. Many have called for stronger real-time monitoring, better communication, and greater accountability.
Why Odors Keep Happening
Odors at the refinery stem from both planned and unplanned operations. Planned events include maintenance shutdowns, startups, and flaring during system transitions. Unplanned events come from equipment malfunctions, power outages, leaks, or sudden upsets in processing units. In both cases, gases may be flared or vented, producing odors that spread with prevailing winds. Weather plays an important role, too. During inversions, when a layer of warm air traps pollutants close to the ground, odors can linger longer and travel farther. Offshore winds can also carry refinery odors inland, directly over neighborhoods.
Regulatory Oversight
The South Coast Air Quality Management District regulates odor and flare events under rules that prohibit public nuisances and require refineries to minimize flaring. Facilities like Chevron El Segundo must report flare activity, emissions, and odor events. Regulators maintain a complaint hotline and deploy inspectors to investigate reports. While enforcement has led to Notices of Violation, critics argue that penalties are often too small to deter repeat incidents. Community members have also pushed for more transparent data sharing, including real-time air monitoring results and public dashboards.
Health and Environmental Effects
Even when short-term odors are not deemed dangerous, repeated exposure contributes to cumulative stress for nearby communities. Sulfur compounds, volatile organic compounds, and particulate matter from flaring can all affect respiratory health, especially for sensitive populations such as children, the elderly, and people with asthma. Long-term impacts of chronic low-level exposure are less well understood but remain a major concern for residents who live in the shadow of the refinery.
Looking Back and Moving Forward
The history of odor events at Chevron El Segundo reflects the challenges of operating a massive refinery within a densely populated urban environment. From the sulfur unit malfunction in 2013 to hydrogen sulfide releases in 2021, from planned maintenance flares to unplanned fire-related flares in 2022 and 2025, the refinery has been the source of recurring smells that shape community perceptions of safety and quality of life. While Chevron has invested in emissions controls and monitoring, the persistence of odor events shows the limits of technology in eliminating every incident. For nearby residents, what matters most is not only whether emissions are technically within limits but whether their lived experience of air quality is respected.
Improving the relationship between the refinery and the community will require proactive steps. This includes minimizing flaring through preventive maintenance and redundancy, installing robust real-time monitoring with public access, notifying residents ahead of planned events, and ensuring rapid investigation and corrective action after odor complaints. Transparency, accountability, and genuine community engagement are essential to addressing not just the science of odors but the trust deficit that decades of smell events have created.
FAQ: Odors at Chevron El Segundo
Why does the refinery smell sometimes? Odors come from sulfur compounds, hydrocarbons, and volatile gases released during flaring, maintenance, or equipment upsets.
Are odors dangerous? Many are detectable at very low levels. While not always harmful, odors can indicate pollutants that at higher concentrations cause respiratory irritation or health risks.
How often do odor events happen? Records show multiple odor events in 2009, 2013, 2021, 2022, and 2025, with both planned and unplanned events reported every few years. Smaller odor complaints are logged more frequently.
Who regulates refinery odors? The South Coast AQMD oversees odors and flaring under nuisance rules and requires Chevron to report events and emissions.
What can be done about refinery odors? Stronger monitoring, advance notice, better combustion systems, and accountability through enforcement can reduce odor events and rebuild trust.
Conclusion
The Chevron refinery in El Segundo has been a cornerstone of California’s fuel supply for more than a century, but it has also been the source of repeated odor complaints from its neighbors. From hydrogen sulfide releases to flaring plumes, odors have been part of the refinery’s history and remain a flashpoint for community concern. As the timeline of events shows, odors are not rare and tend to coincide with maintenance, malfunctions, and emergencies. Moving forward, the challenge for Chevron and regulators is to reduce the frequency and severity of these events while improving communication and trust with residents. For the people who live around the refinery, the smell of oil and sulfur is more than a nuisance—it is a reminder of the costs of living next to one of the nation’s largest industrial operations.
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