A cloudless blue sky, but a greyish mist on the horizon. An episode of air pollution has affected all of France for several days… and the situation is not improving. This Tuesday, February 14, from Rennes to Lille via Lyon and as far as Marseille, 24 cities measured by Atmo (federation of approved associations monitoring air quality) show “bad” air quality. If road traffic and industries contribute to the emission of fine particles, it is above all wood heating which is the main source of this pollution in France.

According to Atmo Auvergne-Rhône-Alpes, this is the major reason for this episode of winter pollution. In the Lyon metropolis, the most affected, differentiated traffic has been in place since Friday February 10 and until at least Tuesday. Only vehicles with a Crit’air 0, 1 or 2 sticker can enter the perimeter of the low emission zone (ZFE), which normally only excludes Crit’air 5 and unclassified vehicles.

The persistence of this episode of generalized pollution is explained by the weather conditions, which do not allow fine particles to be dispersed, starting with the very weak winds which blow over France. Frédéric Nathan, forecaster for Météo-France, also points to temperature inversions: “With clear skies, the temperature cools near the ground at night, while above, the air remains mild. The cold, heavier air thus remains trapped on the ground; pollutants too. Not to mention the anticyclonic conditions, their vertical winds from top to bottom “favoring the plating of pollutants on the ground”, and the dry weather they bring. The pollution could last longer.