On a typical morning in rural Mendocino County, California, Miquette Thompson steps outside and reads the sky the way a sailor reads the sea — except what she is looking for is not weather, but smoke. The Feliz and Woodside fires burning nearby have consumed more than 1,000 acres, and additional smoke drifting south from wildfires in Oregon and Washington has turned the air above her community a persistent, sickly grey. "It's become not unusual," she said. For Thompson, and for the elderly residents and people with respiratory conditions around her, the haze is not an inconvenience but a medical risk: hospitalisation rates for asthma rise by 10% on heavy smoke days, according to a University of California study.

What her local health department failed to communicate clearly — that N95 masks filter fine particles far more effectively than cloth or surgical alternatives — Thompson's own organisation did instead. Her group, Mendo Clean Air Club, partnered with local businesses to distribute N95 masks directly, drawing on years of experience handing out PPE and Covid tests at farmers markets. It is one of more than 40 clean air clubs now operating globally, all tracing their origins to a single initiative launched by Chicago resident Emily Dupree, who began by lending air purifiers to touring musicians during the pandemic. The scale of the need has since grown sharply.

During the catastrophic Los Angeles fires of January 2025, Mask Bloc Los Angeles distributed more than 300,000 masks in just two weeks. Dupree frames what her network does in deliberately political terms. "Covid and climate change are two major pillars of collective denial in the last decade," she said, arguing that the lending libraries were born out of one public failure and are now responding to a second: governments' inability to address worsening air quality and the intensifying wildfire cycle.