A strong chemical odor today at a multi-unit building at 50 Church St. in San Francisco turned a quiet morning into a hazmat scene, sending three residents to medical evaluation and forcing about 20 people out of their homes while fire crews tracked down the source.
Two adults were taken to a nearby hospital with what responders described as non-life-threatening symptoms, and a third person was treated and released at the scene. Residents were ordered to evacuate as firefighters moved in to secure the five-story residential complex and set up a safety perimeter.
According to the SAN FRANCISCO FIRE DEPARTMENT MEDIA, crews were dispatched around 11:40 AM. Fire officials said they confirmed three adult patients, activated hazmat protocols, evacuated roughly 20 occupants, isolated the area, and moved in with protective gear to stop an active leak. Two people were transported to a local hospital for non-life-threatening effects and one was treated and released on site. The department identified the byproduct as sulfur dioxide from an aging refrigeration unit and reported no immediate threat to the general public.
At 11:40 this morning, the San Francisco Fire Department was dispatched to 50 Church St., a five-story multi-residential, multi-unit complex, due to reports of an odor affecting three individuals. Upon arrival, the department confirmed three adult patients—two of whom required… pic.twitter.com/uqbD0Swauj
— SAN FRANCISCO FIRE DEPARTMENT MEDIA (@SFFDPIO) April 17, 2026
Hazmat Response And Evacuation
Firefighters followed standard hazardous-materials protocol: get people out, isolate the area, then go hunting for the source in full protective gear. Occupants were cleared from the building while hazmat crews traced the leak to the refrigeration system and contained it on site.
That quick containment reduced the immediate exposure risk inside the building while investigators and building staff focused on the compromised unit. Building managers and emergency crews stayed on scene to complete air monitoring and ensure the space was safe to reenter.
Health Risks From Sulfur Dioxide
Sulfur dioxide (SO2) is a pungent, colorless gas that can irritate the eyes, nose, and lungs and can make breathing difficult within minutes, especially for people with asthma, according to the U.S. Environmental Protection Agency. Short-term exposure can aggravate chronic respiratory conditions and contribute to the formation of fine particulate matter, which further harms lung function.
Anyone who experiences persistent coughing, chest tightness, or trouble breathing after possible exposure is advised to seek medical attention and tell clinicians about any potential chemical inhalation.
Local Monitoring And What Residents Should Do
The Bay Area Air Quality Management District monitors sulfur dioxide and other pollutants and keeps records of industrial and accidental releases, including flare events. Residents who are worried about local air quality or lingering odors can check BAAQMD data and public notices for neighborhood conditions.
If you notice a strong chemical smell, officials advise avoiding the area, closing windows if it is safe to do so, and calling 911 for emergencies or 311 for non-emergency guidance.
Incident Status
San Francisco fire officials said crews stopped the active leak and kept the response in place into the afternoon while investigators and building maintenance personnel worked to secure the refrigeration system, according to the department's post. The fire department reiterated that there was no known immediate danger to the broader public and urged residents to follow official updates from emergency services and local health authorities.
