Susceptibility to ignition of landscaping mulches exposed to firebrand piles or radiation
Year: 2025
Type: article
Abstract: Mulch products are widely used in landscaping at the wildland-urban interface (WUI), but burning mulch poses a significant ignition hazard to nearby structures. This study evaluates the ignition susceptibility of 10 mulches used in California, USA , exposed to smoldering firebrand piles or irradiation. The mulches included composted types, where products are piled and partially decomposed (bioretention, cal trans, marin vineyard, topper mulch, screened compost) and non-composted types (forest floor, redwood, black mulch, fir bark A and B). We found that all mulches except screened compost can be ignited to smolder by firebrand piles, with ignition more likely at higher firebrand mass and wind speeds . Following spotting ignition, non-composted mulches were more prone to transition from smoldering to flaming at critical wind speeds, which varied by mulch type. For piloted ignition, all mulches can sustain flames under irradiation, with non-composted mulches generally requiring lower critical heat fluxes due to the emission of more combustible gases. Particle size significantly influenced ignition thresholds, with smaller particles facilitating piloted flaming ignition and larger particles being more susceptible to spotting ignition and smoldering-to-flaming transition. This work deepens our understanding of ignition and burning behaviors of mulch, helping improve the prevention and suppression strategies against catastrophic WUI fires.
Source: Fire Safety Journal
Language: English
Subfield: Safety, Risk, Reliability and Quality
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,770
Awards: PURPOSE: THE PURPOSE OF THIS GRANT IS TO DEVELOP A SCIENTIFIC UNDERSTANDING OF THE MECHANISMS BEHIND FIRE SPREAD BY VEGETATION-GENERATED FIREBRANDS. THE RESEARCH WILL PROVIDE THE NECESSARY DATA TO MODEL AND PREDICT THE SPREAD OF WILDLAND FIRES IN COMMUNITIES. ACCURATE MODEL PREDICTIONS WILL FACILITATE RISK MANAGEMENT AND MITIGATION STRATEGIES TO BE IMPLEMENTED.ACTIVITIES TO BE PERFORMED: THE FOLLOWING ACTIVITIES WILL BE PERFORMED. FIRST WIND-TUNNEL WILL BE SET UP TO CONDUCT FIREBRAND IGNITION STUDIES. FIREBRANDS TO BE TESTED WILL BE CHARACTERIZED IN TERM OF THEIR PROPERTIES AND CONCENTRATION FOR IGNITION STUDIES. HEAT TRANSFER MEASUREMENTS FROM MULTIPLE FIREBRANDS ON A TARGET SUBSTRATE WILL BE TAKEN. A RANGE OF SUBSTRATES WILL BE EXPOSED TO MULTIPLE FIREBRANDS TO ASSESS IGNITION PROPENSITY. THE COMBINED RESEARCH MEASUREMENTS WILL PROVIDE A MORE COMPLETE PICTURE OF IGNITION EVENTS AND SUGGEST THE CRITICAL PARAMETERS CONTROLLING IGNITIONS.EXPECTED OUTCOMES: THE EXPECTED OUTCOME IS A MORE COMPLETE PICTURE ON THE MECHANISMS AND IMPORTANT PARAMETERS GOVERNING WILDLAND FIRE EMBER IGNITIONS AND FIRE SPREAD. THE RESEARCH RESULTS MAY LEAD TO MORE APPROPRIATE FIRE SAFETY STANDARDS BY CHARACTERIZING THE THREAT OF FIREBRANDS TO IGNITION OF COMMON BUILDING MATERIALS. AN EMBER IGNITION MODEL DEVELOPED FROM THE RESULTS COULD FACILITATE RISK MANAGEMENT AND MITIGATION STRATEGY APPROACHES FOUNDED ON SOUND SCIENTIFIC KNOWLEDGE. INTENDED BENEFICIARIES: HOMEOWNERS AND OTHERS RESPONSIBLE FOR BUILDINGS IN AREAS PRONE TO WILDLAND FIRES WOULD BENEFIT FROM MORE ROBUST CODES AND STANDARDS TO HARDEN STRUCTURES FROM POTENTIAL IGNITIONS. EMERGENCY MANAGERS AND OTHER COMMUNITY PLANNING PERSONNEL WOULD BENEFIT FROM MODELS TO PREDICT THE EFFECTS OF EMBER IGNITION AND FIRE SPREAD TO DEVELOP MITIGATION STRATEGIES AND RISK MANAGEMENT TO IMPROVE COMMUNITY RESILIENCE. SUBRECIPIENT ACTIVITIES: THE UNIVERSITY OF PORTLAND IS A SUBAWARDEE. UNDER THE DIRECTION OF THE CO-I AT THE UNIVERSITY OF PORTLAND, SEVERAL UNDERGRADUATES WILL PARTICIPATE IN SUMMER RESEARCH TO COLLECT DATA. THE SUBAWARDEE WILL ALSO BE RESPONSIBLE FOR DATA ANALYSIS., G4404116261, G8373352671
OpenAlex ID: W4409478457