Characterizing Wildland Firefighters' Thermal Environment During Live-Fire Suppression.

Wildland firefighters work under adverse environments (e.g., heat and fire exposure), which contribute to increasing the heat strain. Despite this there is a paucity of knowledge about the thermal environment in real wildfire suppression scenarios. Therefore, the main purpose of this study was to characterize the environmental thermal exposure and the risk of heat burn injuries during real wildfire suppression (n = 23). To characterize the wildland firefighter's (n = 5) local thermal exposure, measurements of air temperature and heat flux were performed. Heat flux measurements were made using four thin-planar heat flux sensors. Two were affixed on the outer surface of the garment on the left chest and thigh. Two other sensors were placed on the inner surface of the fabric in parallel to those placed externally. Four thermal classes were defined based on the heat flux across the inner sensors (≤1000, ≤5000, ≤7000, and >7000 W⋅m-2). The risk of pain and first-degree burns were calculated using the dose of thermal radiation method. The inner sensors mean and maximum heat flux and environment temperature were 286.7 ± 255.0 and 2370.4 ± 3004.5 W⋅m-2 and 32.6 ± 8.9 and 78.0 ± 8.9°C, respectively. Approximately 81, 15, and 3.5% of the exposure time the heat flux was ≤1000, >1000-5000, and >5000 W⋅m-2, respectively. The highest average and maximum thermal dose values were ∼94 and ∼110 (kW⋅m-2)4/3⋅s. In conclusion, the thermal exposure obtained may be considered light. However, high thermal exposure values may be obtained in punctual moments, which can elicit first-degree burns.

Fractional Contribution of Wildland Firefighters' Personal Protective Equipment on Physiological Strain.

Activities performed by wildland firefighters are carried out wearing a personal protective equipment (PPE). Although the PPE protects workers from a wide variety of hazards, it may increase their physiological response and limit their performance. The aim of this study was to analyze the effect of the protective clothing (PPC) and the rest of the PPE elements (i.e., helmet, neck shroud, gloves, goggles, and mid-calf leather boots) on the wildland firefighters' thermophysiological response during a moderate-intense exercise. Six male wildland firefighters performed, in a counterbalanced order, a 120 min graded exercise test wearing three different clothing configurations: (i) a traditional short sports gear (SG), (ii) a PPC, and (iii) a complete firefighters' PPE. Trials were conducted on separate days at the same time of the day (12:00-15:00 h) and under climate-controlled conditions (∼30°C and ∼30% relative humidity). Heart rate, respiratory gas exchange, gastrointestinal and skin temperature, blood lactate concentration were recorded throughout the tests. Additionally, parameters of heat balance were estimated. Exercise time was shorter (p < 0.001) wearing the PPE (62.4 ± 13.3 min) than with the PPC (115.5 ± 5.0 min) and SG (118.2 ± 20.7 min). The increment of gastrointestinal temperature with the PPE (1.8 ± 0.3°C) was greater (p < 0.05) than the observed in PPC (1.2 ± 0.6°C) and SG (1.0 ± 0.2°C). The use of PPC increased (p < 0.05) subjects' metabolic demand and skin temperature versus SG during the last 20 min of the test. The sweat retention in the PPE (1,045.7 ± 214.7 g) and PPC (978.3 ± 330.6 g) was significantly higher than that obtained in the SG (510.0 ± 210.0 g). Sweat efficiency decreased (p < 0.05) in the following order: PPE (45.6 ± 18.3%), PPC (64.3 ± 7.8%), and SG (79.3 ± 7.0%). These results highlight the importance of the PPE elements in the subjects' thermal strain. The reduction in the sweat evaporation produced by the PPE, together with the ensemble mass caused a substantial increase in the subjects' thermophysiological response. As a consequence the performance was reduced by ∼50%.

Impact of Different Personal Protective Clothing on Wildland Firefighters' Physiological Strain.

Wildfire firefighting is an extremely demanding occupation performed under hot environment. The use of personal protective clothing (PPC) is needed to protect subjects from the thermal exposure. However, the additional use of PPC may increase the wildland firefighters' physiological strain, and consequently limit their performance. The aim of this study was to analyze the effect of four different PPC on the physiological strain of wildland firefighters under moderate conditions (30°C and 30% RH). Eight active and healthy wildland firefighters performed a submaximal walking test wearing a traditional short sports gear and 4 different PPC. The materials combination (viscose, Nomex, Kevlar, P-140 and fire resistant cotton) used during the PPC manufacturing process was different. During all tests, to simulate a real scenario subjects wore a backpack pump (20 kg). Heart rate, respiratory gas exchange, gastrointestinal temperature, blood lactate concentration, perceived exertion and temperature and humidity underneath the PPC were recorded throughout tests. Additionally, parameters of heat balance were estimated. Wearing a PPC did not cause a significant increase in the subjects' physiological response. The gastrointestinal temperature increment, the relative humidity of the microclimate underneath the PPC, the sweat residue in PPC, the sweat efficiency, the dry heat exchange and the total clothing insulation were significantly affected according to the PPC fabric composition. These results suggest that the PPC composition affect the moisture management. This might be taken into account to increase the wildland firefighters' protection in real situations, when they have to work close to the flames.

Physiological work demands of Spanish wildland firefighters during wildfire suppression.

PURPOSE: The aim of this study was to analyze the physiological demands and thermal strain of wildland firefighters during real wildfire suppression. METHODS: The response of core temperature and heart rate (HR) were analyzed in 200 wildland firefighters during wildfire suppression activities of different duration: <1 h (n = 52), 1-3 h (n = 70), 3-5 h (n = 44), and >5 h (n = 34). The exercise workload (TRIMP), the physiological strain index (PSI), and cumulative heat strain index (CHSI) were calculated using the time spent in different intensity zones, the HR, and core temperature. RESULTS: Mean HR was significantly higher (P < 0.05) in wildfires <1 h (133 ± 2 bpm) and 1-3 h (128 ± 1 bpm) versus 3-5 h (120 ± 3 bpm) and >5 h (116 ± 32 bpm). The time spent in higher intensity zones increased (P < 0.05) when wildfire duration increased. TRIMP accumulation increased with wildfire duration (54.9 ± 3.2, 167.4 ± 5.9, 296.0 ± 8.3, 511.7 ± 12.8 in <1, 1-3, 3-5, and >5 h, respectively). Neither core temperature (37.4 ± 0.1°C) nor PSI (4.5 ± 0.2) were influenced by wildfire duration. The CHSI increased (p < 0.05) in the following order: <1 h (104 ± 23), 1-3 h (1,396 ± 275), 3-5 h (4,586 ± 387), and >5 h (10,703 ± 710). CONCLUSIONS: The results demonstrate the high work strain sustained by Spanish wildland firefighters during wildfire suppression. Both workload and CHSI increased with the wildfires duration although the pace of work was faster in wildfires of a shorter duration.

[Exposure to carbon monoxide in wildland firefighters during wildfires suppression]. / Exposición al monóxido de carbono del personal especialista en extinción de incendios forestales.

BACKGROUND: Health and occupational performance in wildland firefighters are mainly impaired for the carbon monoxide inhalation. Therefore, the aim of this study was to analyze the personal exposure to carbon monoxide in wildland firefighters during wildfires suppression. METHODS: Carbon monoxide exposure was monitorized in 44 subjects during 58 real wildfires. Moreover, we analyzed the time weighted average exposure for an 8h shift (VA-ED). The wildfires were classified according to the work done (direct attack, indirect attack and mixed attack) and the current fuel (grass, bush, understory and mixed). RESULTS: The mean exposure to carbon monoxide was of 18,4 ± 1,7 ppm, what supposed a VA-ED of 7,0 ± 1,0 ppm. The highest exposures to carbon monoxide were found during the mixed attack (20,4 ± 2,3 ppm) and direct attack (17,5 ± 2,7 ppm). We only obtained significant differences (p < 0.05) between bush (19,8 ± 2,2) and understory (17,2 ± 3,9) and grass (12,0 ± 5,6). CONCLUSIONS: Exposures to carbon monoxide were influenced for the work done during the wildfires suppression and the type of fuel involved. Mean values obtained in this study were within safety limits described by different Spanish (INSHT) and international (NIOSH, OSHA) occupational safety and health agencies.

Intensidad de esfuerzo realizado en la extinción de incendios forestales / Exercice intensity during wildfire suppression

El Personal Especialista en Extinción de Incendios Forestales (PEEIF) desarrolla su trabajo en condiciones que exigen un gran esfuerzo físico. La actividad realizada está condicionada por diversos factores, entre ellos las altas temperaturas, la dureza orográfica, la inhalación de humos y la deshidratación. En el presente estudio se ha cuantificado el esfuerzo realizado por el PEEIF (n = 200) en la extinción de diferentes incendios forestales (n = 79). Así, en función del consumo de oxígeno máximo (VO2max) de los sujetos se establecieron tres zonas de intensidad de esfuerzo: moderada (por debajo del 50% VO2max), alta (entre el 50 y el 75% VO2max) y muy alta (por encima del 75% VO2max). El tiempo de permanencia en cada una de estas zonas se utilizó para calcular la carga de trabajo, multiplicando por las constantes 1, 2 o 3, respectivamente. La duración media de los incendios fue de 225,3 ± 6,2 min. La frecuencia cardíaca (FC) media obtenida por los sujetos fue de 117 ± 2 ppm. Los sujetos permanecieron 185,5 ±5,4, 33,1 ± 1,5 y 4,5 ± 0,5 min en la zona de moderada, alta y muy alta intensidad, respectivamente. Cuando se compararon los incendios en función de su duración no se obtuvieron diferencias significativas en el porcentaje del tiempo total de trabajo en la zona de alta intensidad. Sin embargo, a medida que la duración de los incendios fue mayor el porcentaje de trabajo en la zona de moderada intensidad aumentó en detrimento del porcentaje de trabajo a alta intensidad. Se obtuvo una carga de trabajo media de aproximadamente 265 unidades. En conclusión, el esfuerzo desarrollado por el PEEIF en la extinción de incendios fue muy exigente, fundamentalmente debido a la duración delos incendios. El conocimiento de estas demandas puede ayudar al desarrollo de programas de entrenamiento más específicos que permitan afrontar la extinción de los incendios de manera más eficiente y segura (AU)

The wildland firefighters (PEEIF) develop their work inconditions that require great physical effort (eg., high temperature, hardness orographic, smoke exposure, dehydration). The aim of this study was to quantify the exercise effort exerted by the PEEIF (n = 200) in different wildfires extinction (n = 79). According to the maximum oxygen consumption values (VO2max), three intensity zones were established: moderate (below 50% VO2max), high (between50-75% VO2max) and very high (above 75% VO2max). The workload was computed by multiplying the duration of wildfire within each zone by a multiplier for that intensity zone (zone 1 = 1, zone 2 = 2, zone 3 = 3) and reported as TRIMP. The mean duration of the wildfires was 225.3 ±6.2 min and the mean heart rate (HR) 117 ± 2 bpm, representing 60.6 ± 1.1 % of the maximum HR. Subjects spent 185.5 ± 5.4, 33.1 ± 1.5 and 4.5 ± 0.5 min in moderate, high and very high exercise intensity zones, respectively. When we compared wildfires according to its duration, no significant differences in the percentage of total time spentin high intensity zone were found. However, when wildfires duration was higher, the percentage of total time spentin moderate intensity zone increased and the percentage of total time spent in high-intensity zone decreased. The mean workload (TRIMP) was ~265 units. In conclusion, the present study shows that wildfire extinction is highly demanding. It is likely that the workload is modulated by total wildfire duration. Finally, the knowledge of these demands can help to develop more specific and scientific training programs (AU)