Strong mystery odor returns in Costa Mesa and Huntington Beach; officials give mixed responses

A recurrence this week of a strong sulfurous odor spreading through Costa Mesa, Huntington Beach and other local areas brought mixed messages from municipal and air quality officials about the source of the stench.

Twitter users took to the digital platform to ask the South Coast Air Quality Management District and the cities of Huntington Beach and Costa Mesa about the cause of what residents described as a “heavy methane,� “petroleum� or “horribly strong natural gas� odor.

Similar mysterious smells were reported in 2016 and 2017, causing frustrated residents and city officials to demand answers.

The Huntington Beach Fire Department published a statement Tuesday in response to “hundreds of calls� to emergency and non-emergency lines Monday and Tuesday. The department said on Facebook that the “gas smell is a natural occurrence or a methane plume blowing in from offshore.�

Some Facebook users pushed back against the department’s explanation that the smell was caused by naturally occurring methane originating from the ocean floor, noting that the city is not the lead investigative agency on the matter and that the AQMD has refrained from definitively pegging a source.

Costa Mesa officials went on Facebook to retract an earlier claim that offshore oil rigs were to blame for the odor. Officials deferred to an AQMD statement that the source is still undetermined but being investigated.

Municipal social media pages repeatedly directed readers to an undated AQMD odor complaint response that included results from several air quality samples collected between March 1, 2017, and Aug. 14, 2018.

The AQMD document states that “to date, the source(s) of the odors have not been clearly identified, but potential sources are being investigated. There are multiple sources within the area that have the potential to emit gas/sulfur/chemical-type odors, and due to the intermittent nature and unknown source location, it is challenging to assess the cause.�

Officials have maintained that the odors pose no immediate danger to life, though in some instances residents have reported headaches, nausea and sore throats.

Odors can be reported to the AQMD at (800) 288-7664. Any abnormal medical symptoms should be reported to 911, officials said.

Fire authorities said a gaseous smell should be reported to 911 if it is believed to be coming from inside a building.

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