On Tuesday, fires continued their widespread destruction across much of the West, taking advantage of tinder-dry brush and undergrowth primed for disaster by the increased temperatures and dryness from climate change. Smoke made the air over Portland the worst in the world, and the San Francisco Bay Area set a local record after nearly a month of hazardous air quality alerts — conditions that research has linked to health problems The firefighters rely on techniques developed over the decades to hold fires at bay. "Along with using helicopters and tanker aircraft to drop the water and flame retardant, there is arduous labor on the ground. Some of it requires carefully burning areas in the path of an advancing fire to try to rob it of the fuel it needs to keep progressing. It can also involve dousing flames with water brought in by truck — or, in rough country, hiked in along with hoses and pumps" "At the most fundamental, though, it means workers using hand tools to dig the fire lines — the borders, cleared of trees and shrub, that can stop a fire from advancing by removing all vegetation and scraping down to the “mineral soil,” the bare dirt"