The Marshall Fire burned entire housing estates and shopping malls. Are ashes a threat to air quality?

Since the Marshall fire, many residents have been concerned about odor hints of a lingering air quality risk. The fast-moving blaze started in grassy open spaces and ignited urban areas, consuming more than a thousand buildings made from particle board, plastic, metals and other materials. Other products inside, from paint to cleaning solvents, also burned.

It’s unclear if all of these synthetic remains pose an immediate threat to people in or near the burnt area. Researchers from NOAA and the University of Colorado at Boulder rushed in the aftermath of the fire, launching studies to monitor indoor and outdoor air quality. Their results could affect how quickly and safely residents can return and rebuild.

Warneke was relieved by early results on his first drive through Louisville. A computer screen in the passenger seat showed low levels of dangerous airborne toxins like benzene. The biggest spike came as he drove past a truck pumping out exhaust on a road outside the neighborhood.

“Looking at the concentrations, I wouldn’t be too worried at this point, but we haven’t analyzed the data in detail yet,” he said.

Sam Brasch/CPR News
National Oceanic and Atmospheric Administration researcher Carsten Warneke drives an air monitoring van through Louisville’s Harper Lake neighborhood, which was devastated by the Marshall Fire.

An air of uncertainty

The NOAA team took action at the request of Boulder County Public Health. Since the Dec. 30 fire, the county has issued a changing set of recommendations based on its current understanding of the health risk.

The first set of guidelines advised people in the burnt area or living downwind to avoid outdoor exercise. On Friday, he issued a statement with an updated set of recommendations. He asks anyone with a respiratory illness to wear an N95 mask in the burnt area.

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