PITTSBURGH (KDKA) – The state Department of Environmental Protection has issued a Code Orange Air Quality Action Day for parts of Allegheny County on Christmas Eve ad Christmas.

The DEP says it is forecasting a Code Orange Air Quality Action Day on Dec. 24 and Dec. 25 for the Liberty-Clairton area in Allegheny County.

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A “strong morning inversion” will produce stagnant air Tuesday, the DEP says, and the averages for fine particulate matter will be in the Code Orange range. On Wednesday, a ridge of high pressure will remain, allowing for a strong inversion to form over Pennsylvania.

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A Code Orange means there’s an unhealthy pollution level for sensitive people, the DEP explains.

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The DEP says on air quality action days, young children, the elderly and people with respiratory problems are especially vulnerable to air pollution. It’s recommended they limit their outdoor activities.