A large warehouse fire in Northern California continues into its third day, with officials reporting deteriorating and unhealthy air quality due to smoke. Fire crews remain engaged in an extended effort to contain and put out the blaze inside the building. Authorities warn that conditions are expected to stay smoky for the next few days, reflecting the length of the firefighting operation. Health guidance focuses on residents who are more sensitive to smoke, urging them to remain indoors and limit exposure. The warnings are directed particularly at people likely to experience health effects from poor air, including those with respiratory or heart conditions and others advised by public health agencies. Firefighters are described as continuing their work through Saturday, indicating the fire is not fully contained yet. While the sources emphasize the ongoing smoke and public health guidance, they do not provide consistent details about the cause of the fire, the extent of damage, or the status of any evacuations beyond the advice to reduce exposure to smoke.