From the Setting Guide

The city of Shadar is one of the oldest in the Dusk Empire.

Also known as the city of ash, the excavation of coal lead to an industrial boom in the city, which in turn lead to some of the Empire’s first learning institutions.

The city is best known now for the Nightfall Military Academy, the premier military school in the Jewel Cities.

The Ash Cloud

The aggressive extraction of coal for miles around the city kicks up a permanent cloud of ash and dust which hangs over the city.

Masks have become a common part of life in Shadar, as the citizens attempt to protect their lungs from the coal ash and smoke of the industrial area.

Common folk use simple strips of cloth, sometimes treated with medicinal herbs (+1 counteract, 5sp), whereas the legionnaires wear sealed masks (+2 counteract, 1gp cost) and nobles and senior military will be equipped with full filter masks (+5 counteract, 10gp)