Cell2Fire: A Cell-Based Forest Fire Growth Model to Support Strategic Landscape Management Planning

Cell2Fire is a new cell-based wildland fire growth simulator designed to integrate data-driven landscape management planning models. The fire environment is modeled by partitioning the landscape into cells characterized by fuel, weather, moisture content, and topographic attributes. The model can use existing fire spread models such as the Canadian Forest Fire Behavior Prediction System to model fire growth. Cell2Fire is structured to facilitate its use for predicting the growth of individual fires or by embedding it in landscape management simulation models. Decision-making models such as fuel treatment/harvesting plans can be easily integrated and evaluated. It incorporates a series of out-of-the-box planning heuristics that provide benchmarks for comparison. We illustrate their use by applying and evaluating a series of harvesting plans for forest landscapes in Canada. We validated Cell2Fire by using it to predict the growth of both real and hypothetical fires, comparing our predictions with the fire scars produced by a validated fire growth simulator (Prometheus). Cell2Fire is implemented as an open-source project that exploits parallelism to efficiently support the modeling of fire growth across large spatial and temporal scales. Our experiments indicate that Cell2Fire is able to efficiently simulate wildfires (up to 30x faster) under different conditions with similar accuracy as state-of-the-art simulators (above 90% of accuracy). We demonstrate its effectiveness as part of a harvest planning optimization framework, identifying relevant metrics to capture and actions to mitigate the impact of wildfire uncertainty.

Integration of a Coupled Fire-Atmosphere Model Into a Regional Air Quality Forecasting System for Wildfire Events

The objective of this study was to assess feasibility of integrating a coupled fire-atmosphere model within an air-quality forecast system to create a multiscale air-quality modeling framework designed to simulate wildfire smoke. For this study, a coupled fire-atmosphere model, WRF-SFIRE, was integrated, one-way, with the AIRPACT air-quality modeling system. WRF-SFIRE resolved local meteorology, fire growth, the fire plume rise, and smoke dispersion, and provided AIRPACT with fire inputs. The WRF-SFIRE-forecasted fire area and the explicitly resolved vertical smoke distribution replaced the parameterized BlueSky fire inputs used by AIRPACT. The WRF-SFIRE/AIRPACT integrated framework was successfully tested for two separate wildfire events (2015 Cougar Creek and 2016 Pioneer fires). The execution time for the WRF-SFIRE simulations was <3 h for a 48 h-long forecast, suggesting that integrating coupled fire-atmosphere simulations within the daily AIRPACT cycle is feasible. While the WRF-SFIRE forecasts realistically captured fire growth 2 days in advance, the largest improvements in the air quality simulations were associated with the wildfire plume rise. WRF-SFIRE-estimated plume tops were within 300-m of satellite-estimated plume top heights for both case studies analyzed in this study. Air quality simulations produced by AIRPACT with and without WRF-SFIRE inputs were evaluated with nearby PM2.5 measurement sites to assess the performance of our multiscale smoke modeling framework. The largest improvements when coupling WRF-SFIRE with AIRPACT were observed for the Cougar Creek Fire where model errors were reduced by ∼50%. For the second case (Pioneer fire), the most notable change with WRF-SFIRE coupling was that the probability of detection increased from 16 to 52%.

Residential Flashover Prevention with Reduced Water Flow: Phase 2

The purpose of this study was to investigate the feasibility of a residential flashover prevention system with reduced water flow requirements relative to a residential sprinkler system designed to meet NFPA~13D requirements. The flashover prevention system would be designed for retrofit applications where water supplies are limited. In addition to examining the water spray's impact on fire growth, this study utilized thermal tenability criteria as defined in UL 199, Standard for Automatic Sprinklers for Fire-Protection Service. The strategy investigated was to use full cone spray nozzles that would discharge water low in the fire room and directly onto burning surfaces of the contents in the room. Where as current sprinkler design discharges water in a manner that cools the hot gas layer, wets the walls and wets the surface of the contents in the fire room. A series of eight full-scale, compartment fire experiments with residential furnishings were conducted with low flow nozzles. While the 23~lpm (6~gpm) of water was the same between experiments, the discharge density or water flux around the area of ignition varied between 0.3~mm/min (0.008~gpm/ft**2) and 1.8~mm/min (0.044~gpm/ft**2). Three of the experiments prevented flashover. Five of the experiments resulted in the regrowth of the fire while the water was flowing. Regrowth of the fire led to untenable conditions, per UL 199 criteria, in the fire room. At approximately the same time as the untenability criteria were reached, the second sprinkler in the hallway activated. In a completed system, the activation of the second sprinkler would reduce the water flow to the fire room, which would potentially lead to flashover. The variations in the burning behavior of the sofa resulted in shielded fires which led to the loss of effectiveness of the reduced flow solid cone water sprays. As a result of these variations, a correlation between discharge density at the area of ignition and fire suppression performance could not be determined given the limited number of experiments. An additional experiment using an NFPA~13D sprinkler system, flowing 30~lpm (8 gpm), demonstrated more effective suppression than any of the experiments with a nozzle. The success of the sprinkler compared with the unreliable suppression performance of the lower flow nozzles supports the minimum discharge density requirements of 2~mm/min (0.05~gpm/ft**2) from NFPA~13D. The low flow nozzle system tested in this study reliably delayed fire growth, but would not reliably prevent flashover.

A Prediction Model of Casualties Based on Machine Learning for Selection of Fire Scenario

This study has developed a model that predicts casualties (dead and injured people) using the Classification And Regression Tree (CART). Based on the fire statistics collected over a decade, this model aims to select the appropriate risk-assessment scenarios and fire prevention and safety methods applicable on individual buildings. Our evaluation indicates that this CART model can accurately predict 48 scenarios based on 5 variables related to the types of fire, fire growth rates, and evacuation situations, and calculate the corresponding probabilities for each occurrence. This model is expected to improve future quantitative fire risk assessments.

Modeling of the Heat Release Rate Curve of Rigid Plastic Combustibles Based on their Geometrical Properties and Constituent Materials

In this study, we conducted the modeling and generalization of the heat release rate of rigid plastic combustibles with respect to their geometrical properties. The modeling and generalization was carried out using the model proposed by Natori, which is based on the combustion behavior of wooden furniture. Previous studies that have reported the combustion of printers were used for the modeling of the heat release rate of rigid plastic combustibles. The reported heat release rate measurements of the printers were examined to determine their applicability to Natori's model. After their applicability was confirmed, to generalize the heat release rate curve, heat release rate parameters of the combustibles were analyzed with respect to their geometrical properties and constituent materials. The combustibles were classified into two groups based on their geometrical properties, and the fire growth rate, maximum heat release rate, and decay rate represented the heat release rate parameters. Furthermore, the parameters were analyzed as a function of the apparent density of the combustibles. The fire growth rate and maximum heat release rate exhibited a relatively evident correlation with the apparent density, which indicated that an accurate estimation of the heat release rate curve can be obtained from the external dimensions and weight of the combustibles.

Weather Factors Associated with Extremely Large Fires and Fire Growth Days

Abstract“Megafires” are of scientific interest and concern for fire management, public safety planning, and smoke-related public health management. There is a need to predict them on time scales from days to decades. Understanding is limited, however, of the role of daily weather in determining their extreme size. This study examines differences in the daily weather during these and other, smaller fires, and in the two sets of fires’ responses to daily weather and antecedent atmospheric dryness. Twenty fires of unusual size (over 36 400 ha), were each paired with a nearby large fire (10 100 to 30 300 ha). Antecedent dryness and daily near-surface weather were compared for each set of fires. Growth response to daily weather was also examined for differences between the two sets of fires. Antecedent dryness measured as the Evaporative Demand Drought Index was greater for most of the fires of unusual size than it was for smaller fires. There were small differences in daily weather, with those differences indicating weather less conducive to fire growth for the unusually large fires than the smaller fires. Growth response was similar for the two sets of fires when weather properties were between 40th and 60th percentiles for each fire pair, but the unusually large fires’ growth was observably greater than the smaller fires’ growth for weather properties between the 80th to 100th percentiles. Response differences were greatest for wind speed, and for the Fosberg Fire Weather Index and variants of the Hot-Dry-Windy Index, which combine wind speed with atmospheric moisture.

A Numerical Study for Assessing the Risk Reduction Using an Emergency Vehicle Equipped with a Micronized Water System for Contrasting the Fire Growth Phase in Road Tunnels

We performed Computational Fluid Dynamics (CFD) modeling, and simulated a people evacuation process from a tunnel in the event of a fire, for evaluating the potentialities of using, as a temporary safety measure, an emergency vehicle equipped with a micronized water system for contrasting the fire growth phase. The structure investigated is a one-way road tunnel with only natural ventilation, and with a length less than 1000 m. The tunnel is assumed at present to be affected by refurbishment works for making it comply with the minimum safety requirements of the European Directive 2004/54/EC. In particular, it is considered that it has not yet been provided with hydrants, and with the sidewalks and the emergency exit which are still under construction. This means that users are forced to use the road carriageway for escaping from the tunnel if a fire occurs. The CFD findings have shown that the use of the micronized water system might lead to a significant improvement in the environmental conditions along the escape route since the tenability limits of temperature, radiant heat flux, CO and CO2 concentration were found to be better satisfied. Additionally, the visibility distance was shown to increase, even though it was found to be higher than the acceptable threshold value only in a few cases. However, the quantitative risk analysis based on a probabilistic approach, which was combined with a method currently used in Europe for assessing the risk due to the transit of only dangerous goods, shows that the final cumulative F-N curves related to the micronized water system always lie below those without the mentioned system, and in addition, they are always contained within the limits of the ALARP region. It is to be stressed that our paper might represent a reference in showing the effectiveness of the micronized water system as a temporary safety measure. However, it is desirable that the Tunnel Management Agencies accelerate the refurbishment works for making road tunnels definitively safer for users in a short period of time.

Fire Growth Rate Index as a Key Fire Characteristic of Electrical Cables

This study deals with the Fire Growth Rate Index (FIGRA) as a key fire characteristic of electrical cables (determined by a cone calorimeter) that allows to estimate their reaction to fire class. Three power (supply) electrical cables (reaction to fire class B2ca) were tested by a cone calorimeter using different heat fluxes of 20, 30, 40 a 50 kW·m−2. The cables were three-wire (cross-section of each wire was 1.5 mm2) with a nominal voltage of 0.6 kV (alternating current), resp. 1 kV (direct current). The cable sheaths were made of an ethylene copolymer filled with aluminum hydroxide. The beddings were made of an ethylene copolymer filled with a mixture of aluminum hydroxide and calcium carbonate. The conductor insulations of one electrical cable were made of crosslinked polyethylene and the conductor insulations of the other two electrical cables were made of an ethylene copolymer filled with aluminum hydroxide. FIGRA was determined per unit length and unit area of electrical cables. FIGRA increased with increasing heat flux. At a heat flux of 50 kW·m−2, all the electric cables examined showed a very similar FIGRA (from 0.19 to 0.21 kW·m−1·s−1 and 18.4 to 21.2 kW·m−1·s−1, respectively). Conversely, at a heat flux of 20 kW·m−2, the investigated cables showed greater FIGRA variance (in the range of 0.11 to 0.16 kW·m−1·s−1 or 10.8 to 16.2 kW·m−1·s−1).

Effects of Time to Unactuate Air Conditioning on Fire Growth

Air conditioning systems have become essential equipment in many buildings. However, fire safety design and management in buildings rarely consider whether to turn the system off or keep it on in a fire. This study ignites a stack of wood in a room center or corner to explore the influence of air inlet actions of a fan coil unit (FCU) with the door opened or closed. Simulation results using Fire Dynamics Simulator (FDS) demonstrate that the heat release rate (HRR) and room temperature obviously decrease when the room doorway is closed, regardless of whether the air conditioner is turned on. The air supply for combustion is poor. When the door of the room is opened, turning off the air conditioner can effectively reduce the HRR and the room temperature in the early stages of fire growth. However, along with the fire growth, turning on air conditioning can help decrease the heat radiation feedback and the consequent HRR. Therefore, the conclusion that air conditioning always enhances a fire because it provides oxygen may not always be correct.