Officials in southern California are advising some residents against leaving their homes as wildfire smoke worsens air quality in the region.

On Monday afternoon, the National Weather Service (NWS) office in San Diego broadcast an air quality alert from the South Coast Air Quality Management District (AQMD). The alert warned of increased fine particle pollution from wildfire smoke across parts of southern California, and it is expected to remain in place until 11 p.m. local time Tuesday.

“If you smell smoke or see ash due to a wildfire, remain indoors with windows and doors closed or seek alternative shelter, if feasible,” the alert said. “Avoid vigorous physical activity and run your air conditioner and/or an air purifier. If possible, do not use whole house fans or swamp coolers that bring in outside air. Avoid burning wood in your fireplace or firepit and minimize sources of indoor air pollution such as candles, incense, pan-frying, and grilling.”