Harrisburg – The Department of Environmental Protection (DEP) and its regional air quality partnerships have forecast a Code Orange Air Quality Action Day on Saturday, Feb. 1, due to the unseasonably warm air mass moving in this weekend.

DEP and the partnerships urge residents sensitive to air pollution to limit outdoor activity on days when an action has been issued for their region. The Air Quality Action Day for fine particles includes the Philadelphia area, consisting of Bucks, Chester, Delaware, Montgomery and Philadelphia Counties, a state news release said.

On Air Quality Action Days, young children, the elderly and those with respiratory problems are especially vulnerable to the effects of air pollution and should limit outdoor activities, the release said.

The U.S. Environmental Protection Agency’s standardized air quality index uses colors to report daily air quality. Green signifies good; yellow means moderate; orange represents unhealthy pollution levels for sensitive people; and red warns of unhealthy pollution levels for all, the release said.

Fine particulate matter becomes elevated when pollution from vehicles, industry, households and power plants combine with moisture droplets in the air and become trapped near the surface. During cold weather, fine particles rise when there is limited mixing from light winds near the surface, the release said.

These forecasts are provided in conjunction with the Air Quality Partnership of the Delaware Valley, the Southwest Pennsylvania Air Quality Partnership, the Lehigh Valley/Berks Air Quality Partnership and the Susquehanna Valley Air Quality Partnership. For more information, visit http://www.ahs2.dep.state.pa.us/aq_apps/aqpartners/default.asp.