Structural Firefighter Research Articles

Fabrication of Laminated Electrospun Fire˗Resistant Phosphorylated Poly(Vinylalcohol) Membrane for Enhanced Firefighter Safety

AbstractThe current study focuses on the creation of breathable and fire˗retardant fibrous membranes using phosphorylated poly(vinylalcohol) (PPVA) via the electrospinning method, with a specific interest in their application for structural firefighter clothing. Poly(vinylalcohol) (PVA) was phosphorylated to enhance its inherent flame resistance. Optimization of reaction conditions, including time and temperature, was conducted to achieve a solution suitable for electrospinning. The flame resistance of PPVA was confirmed through vertical flammability tests, with thermogravimetric analysis indicating a significant increase in carbonaceous char formation during PPVA decomposition compared to unmodified PVA. The limiting oxygen index also exhibited a notable increase from PVA to PPVA. Furthermore, the study established optimal operating conditions for producing uniform fibers, considering parameters such as polymer concentration, feed rate, tip to collector distance, and applied potential difference. The PPVA membrane demonstrated superior water vapor transmission rates compared to PVA, indicating enhanced breathability. The entire fabrication process utilized an environmentally friendly water‐based solvent. Additionally, a moisture‐cum‐thermal barrier layer (MCTB) was developed by laminating the PPVA fibrous membranes with microporous polytetrafluoroethylene and further with needle punch‐spunlaced OPAN fabric. Experimental assessments of the MCTB layer revealed satisfactory breathability and thermal performance, surpassing the standard requirements of 35 cal/cm2 for structural firefighting configuration.

Heart rate dynamics during a simulated fireground test: The influence of physical characteristics and fitness1.

Firefighting is a physiologically demanding occupation and there is a need to evaluate physical and fitness characteristics that are related to attenuated physiological stress during fireground tasks. Previous studies have not measured associations between heart rate responses during simulated fireground tasks with a standardized work rate. The purpose of this study was to examine associations between heart rate during a standardized pace simulated fireground test (SFGT) and heart rate recovery and variability following the SFGT. In addition, this study sought to evaluate associations between heart rate measures versus physical and fitness characteristics in structural firefighter recruits. Twenty-one fire academy recruits performed a standardized pace SFGT while mean heart rate reserve (HRRes) during the SFGT, change in heart rate variability from rest to post-SFGT (LnRMSSDRest-Post), and 60-second post-SFGT heart rate recovery (HRR60) were measured. Regression analyses were conducted between HRRes, LnRMSSDRest-Post and HRR60 and between heart rate measures versus physical and fitness characteristics while accounting for differences in SFGT completion time. HRRes was associated with LnRMSSDRest-Post, but not HRR60. Height and pull-ups explained most of the variance in HRRes, height explained most of the variance in LnRMSSDRest-Post and push-ups and 1.5-mile run explained most of the variance in HRR60. Greater cardiovascular stress during fireground tasks is associated with greater depression of post-SFGT heart rate variability, but not heart rate recovery. Physical and fitness characteristics are important to consider in relation to firefighters' ability to cope with physical stress on the fireground.

Ergonomic Assessment of Structural Firefighter Turnout Suit Designs for Improved Mobility

The purpose of this study was to design a novel turnout suit for improved mobility based on firefighter user needs. A wear trial assessment was performed to investigate the differences in range of motion (ROM), ease of movement, and comfort of a novel structural firefighter turnout suit versus existing suit models on the market today. Ten healthy firefighters wore three different turnout suits while their ROM was measured using electro-goniometers worn against the skin in the shoulder, elbow, hip, and knee joints. Perceived ease of movement ratings were gathered for 13 static joint exercises. A subjective perception survey was administered after completing the static protocol in each suit. A dynamometer measured peak force and torque in the elbow, knee, and shoulder joints. Results indicate significant differences occurred between the suits for perceived ease of movement ratings and hip ROM.

Effects of Temperature and Advanced Cleaning Practices on the Removal of Select Organic Chemicals from Structural Firefighter Gear

There are approximately 1.2 million firefighters in the United States. In addition to fighting fires, they also participate in various tasks including emergency rescues, providing emergency medical care, driving, operating and maintaining fire vehicles and other apparatuses and continued training. During the course of their duties, firefighters are often exposed to carcinogenic chemicals that may accumulate on their turnout clothing. To determine if these chemicals can be removed and to measure the efficacy of current cleaning protocols, a study was developed to assess these protocols which call for a maximum water temperature of 105°F and no solvents. The results showed that volatile and small semi-volatile chemicals such as dimethyl phthalate and chlorinated phenols had cleaning efficiencies of 85% or greater. However, for polycyclic aromatic hydrocarbons (PAHs), the cleaning efficiency was only 20% to 50%. To determine if it is possible to remove the more persistent PAHs, temperatures were increased to 125°F and 140°F, and a respective increase in cleaning efficiencies of the PAHs was seen. The protocols were then adapted to add a pre-soak cycle which, when combined with the increased temperatures, resulted in an increase of the PAH cleaning efficiency range from 50 to 80%, compound dependent. This work provides a starting point for discussions between the National Fire Protection Association (NFPA) and other standards organization and manufacturers to determine if increased temperatures and chemical soaks would be detrimental to gear as they are currently not advised.

Structural firefighter personal protective clothing user needs in the US: a mobility perspective

Structural firefighter personal protective clothing user needs in the US: a mobility perspective

The Validity and Reliability of a Treadmill Test for Structural Firefighter Applicants.

This 2-part study evaluated validity and reliability of a treadmill test for structural firefighters. Wearing fire protective ensemble, 260 participants walked at 1.56 m·s-1, completing a 5-min warm-up, an 8-min stage at a 5.71° incline, then graded stages to exhaustion. In Part 2, 21 participants completed the test on 3 separate days under standardized conditions. Average (±SD) oxygen uptake () during minutes 1-13 was similar to reported values for simulated fire-rescue work. During the 13th min, was consistent with recommendations for firefighters. in Part 2, exercise duration increased between trials 1 and 2 before stabilizing but was consistent. Congruence with reported during simulated firefighting and recommendations for confirmed validity. Acceptable test-retest reliability was demonstrated. We conclude that the test is valid and reliable for evaluating cardiorespiratory endurance for firefighting.

Identifying factors that contribute to structural firefighter heat strain in North America

This article describes results from a survey of firefighters designed to identify conditions that contribute to heat strain in structural firefighting. Based on responses from about 3000 firefighters across the USA and Canada, the article provides invaluable information about how firefighters associate environmental conditions, work tasks and other factors with heat strain. One-half of firefighters surveyed have experienced heat stress during their service. They can wear fully deployed turnout gear for 2 h or more at the fire scene, reinforcing the importance of turnout suit breathability as a factor in heat strain. Survey results are useful in weighing the comparative value of total heat loss (THL) and evaporative heat resistance (Ref) for predicting turnout-related heat strain. Survey findings support the inclusion of a performance criterion in the National Fire Protection Association 1971 standard for firefighter personal protective equipment based on limiting Ref of turnout materials along with current THL requirement.

Effects of environmental temperature and humidity on evaporative heat loss through firefighter suit materials made with semi-permeable and microporous moisture barriers

The goal of this research was to understand how firefighter protective suits perform in different operational environments. This study used a sweating guarded hotplate to examine the effect of environmental temperature (20–45°C) and relative humidity (25–85% RH) on evaporative heat loss through firefighter turnout materials. Four firefighter turnout composites containing three different bi-component (semi-permeable) and one microporous moisture barriers were selected. The results showed that the evaporative resistance of microporous moisture barrier systems was independent of environmental testing conditions. However, absorbed moisture strongly affected evaporative heat loss through semi-permeable moisture barriers coated with a layer of nonporous hydrophilic polymer. Moisture absorption in mild environment (20–25°C) tests, or when testing at high humidity (>85% RH), significantly increased water vapor transmission in semi-permeable turnout systems. It was also found that environmental conditions used in the total heat loss (THL) test (25°C and 65% RH) produced moisture condensation in bi-component barrier systems, making them appear more breathable than could be expected when worn in hotter environments. Regression models successfully qualified the relationships between moisture uptake levels in semi-permeable barrier systems and evaporative resistance and THL. These findings reveal the limitations in relying on THL, the heat strain index currently called for by the NFPA 1971 Standard for Structural Firefighter personal protective equipment, and supports the need to measure turnout evaporative resistance at 35°C (Ret), in addition to THL at 25°C.

A Survey of Structural Firefighter Station Wear in the United States

Structural turnout gear is essential for the safety of firefighters. The station wear, or clothing worn underneath the structural turnout suit, contributes to the thermal protection and performance of the overall ensemble. Depending on the fiber content and material fabrication, base layer garments may increase the risk of potential burn injuries. The purpose of this research was to evaluate National Fire Protection Association (NFPA) 1975 certified, certified flame resistant, and non-certified station wear garments in relation to firefighter burn injuries while worn under a NFPA 1971 structural firefighting ensemble. An information-gathering questionnaire was distributed nationwide with over 1800 active-duty United States firefighting personnel responding to questions regarding the selection and use of their station wear. Responses concerning the thermoplastic nature of base layer materials, the design and configuration of how base layers are worn, and the overall satisfaction with the performance of certified versus non-certified station wear were gathered. Questionnaire responses determined 80% of participants were aware of the overall risk of wearing non-certified base layer garments (i.e. synthetics that will melt or drip); however, 45% of career firefighters indicated they were not required to wear certified or flame resistant station wear. Regional analysis of the responses was performed. Findings of this research will educate the fire service and inform NFPA standards committees. Further, this study supports the need for future research to develop station wear garments with improved burn injury protection, thermal comfort, and ergonomic mobility.

The Effect of Personal Protective Equipment on Firefighter Occupational Performance.

Lesniak, AY, Bergstrom, HC, Clasey, JL, Stromberg, AJ, and Abel, MG. The effect of personal protective equipment on firefighter occupational performance. J Strength Cond Res 34(8): 2165-2172, 2020-The purpose of this study was to evaluate the effects of load carriage (LC) and LC plus respirator use (LC + self-contained breathing apparatus [SCBA]) on firefighters' work capacity to enhance our understanding of occupational demands. Twenty-one male structural firefighter recruits (age: 28.6 ± 4.3 years; height: 178.6 ± 7.2 cm; body mass: 94.1 ± 15.4 kg; body fat: 22.9 ± 6.1%) participated. Occupational performance was assessed by time to complete a simulated fire ground test (SFGT). After 2 familiarization trials, recruits performed the following SFGT conditions in a randomized order: PT (physical training clothes), LC only, and LC + SCBA. To describe within-group differences between SFGT conditions, relative difference scores were calculated as follows: % difference = ([experimental trial outcome - PT trial outcome]/PT trial outcome) × 100. Statistical differences between conditions were assessed with repeated-measures analysis of variance. The level of significance was set p < 0.01. Time to complete the LC + SCBA trial (345.9 ± 43.7 seconds; p < 0.001) and LC-only trial (331.2 ± 39.3 seconds; p < 0.001) were significantly greater than the PT trial (241.0 ± 33.3 seconds). Post-SFGT rating of perceived exertion was higher in the LC + SCBA trial (6.7 ± 1.7) and LC trial (6.4 ± 1.5) compared with the PT trial (4.7 ± 1.8; p < 0.001). Heart rate and lactate measures were similar across conditions (p = 0.488; p = 0.287). Personal protective equipment (PPE) significantly decreases the work capacity and increases the perceived effort of occupational tasks. Thus, these findings describe the additional physical demands produced by PPE and indicate that performance of firefighting tasks in an unloaded condition does not reflect work capacity in a bona fide condition.

Exertional Strain and Task Performance Consequences of a Reduction in Protection in Structural Fire Fighter PPE - A Pilot Study

Exertional Strain and Task Performance Consequences of a Reduction in Protection in Structural Fire Fighter PPE - A Pilot Study

Firefighter Turnout Suit Weight Influences Simulated Exercise Performance

PURPOSE: To investigate how structural firefighter protective ensemble weight influences rate of perceived exertion (RPE) during firefighter simulated exercise (FFSE). METHODS: 10 active firefighters (age: 33±6 years, Ht:178.2±3.1 cm, Wt:78.6±16.7 kg) were asked to wear, in random order, two ensembles: 1) a single layer (SL) outer shell (2.45 kg) and 2) a traditional turnout suit (4.57 kg). On each laboratory visit, the firefighters performed the FFSE that consisted of two rounds of a 15.24m hose advance, a 15.24m weighted (40.83 kg) carry, sledge hammer exercise, a 15.24m tire flip, a 15.24m dummy drag, rope pull, and unweighted stair climb, with a 1-minute rest period between rounds. The FFSE included a 5-minute acclimation period in the ensemble, a warm up (10 pushups, 10 squats, 20 jumping jacks). Subjects were asked to complete the FFSE as fast as possible. The traditional turnout suit consisted of an outer shell, moisture barrier, and thermal barrier typically found in most turnout suits. The Borg rating of perceived exertion scale was asked immediately at the end of each round of FFSE and ensemble weights were measured pre-FFSE. RESULTS: The SL resulted in lower average RPE for round 1 (SL: 12.8±1.7 vs. Traditional: 13.8±1.7; p=0.05) and round 2 (SL: 14.2±1.6 vs. Traditional: 16.2±2.3, p=0.01) than the traditional turnout. In addition, round 2 of the FFSE was completed significantly faster than the traditional turnout suit (SL: 262.8±55.7 vs. Traditional: 293.4±64.9 sec; p =0.02). CONCLUSIONS: The weight of the turnout suit increases RPE, which appears to influence performance for FFSE. Supported by Fire-Dex, LLC.

The effect of structural firefighter protective clothing systems on single-legged functional hop test scores.

Firefighters must complete a physical ability test to assess work readiness. There is a lack of understanding of how personal protective clothing (PPC) affects functional performance tests for work readiness, e.g. Triple Hop for Distance (THD) and Triple Hop for Work (THW). To examine firefighter PPC's effect on the THD and THW measures. Thirty-one healthy, untrained participants (male = 20, female = 11; age = 23±3 years; height = 175.30± 11.12 cm; mass = 77.94±14.24 kg; mass in PPC = 89.14±14.68 kg) completed three successful trials of the THD on their dominant and non-dominant leg, with and without PPC. The main outcome measures included maximum and mean distances on the THD with and without PPC and THW. We identified a significant decrease in THD measures (mean difference = 97.83 cm; p < 0.001) and THW measures (mean difference = -326.61J; p < 0.001) when donning PPC in the dominant leg. We identified a significant decrease in THD (mean difference = 121.48 cm; p < 0.001) and THW (mean difference = 493.15J; p < 0.001) for females, and a significant difference for THD (mean difference = 84.83 cm; p < 0.001) for males when donning PPC. The addition of PPC decreased the THD and THW measures. The additional mass of the PPC required the more energy to move the same distance without the PPC.

The Effect of Personal Protective Equipment on Firefighter Occupational Performance

PURPOSE: To determine the effect of load carriage (LC) and the self-contained breathing apparatus (SCBA) on occupational performance of structural firefighters. METHODS: Twenty-one professional male structural firefighter recruits (Age: 28.6 ± 4.3 yr; Height:178.6 ± 7.2 cm; Body mass: 94.1 ± 15.4 kg; Body fat: 17.8 ± 8.4%) participated in the study. Occupational physical ability was assessed by time to complete a simulated fire ground test (SFGT). The SFGT was composed of a stair climb, charged hose drag, equipment carry, ladder raise, forcible entry, search, and victim rescue. Subjects performed 2 familiarization trials and 3 trials of a SFGT in different conditions: physical training clothes only (PT), wearing turnout gear and an SCBA (but not breathing through the SCBA (LC)), and wearing turnout gear and breathing through the SCBA (SCBA). RPE was also measured. Heart rate, blood lactate, and perceived exertion were assessed during the SFGT. Repeated measures ANOVAs were used to identify differences among trials. To describe within group changes, relative difference scores were calculated as follows: % difference = (([experimental trial outcome – PT outcome]/ PT outcome) x 100). RESULTS: The SCBA trial took 44.5 ± 15.5% longer (345.9 ± 43.7s; p<.001) and the LC trial took 38.3 ± 12.6% longer (331.2 ± 39.3s; p<.001) than the PT trial (241.0 ± 33.3s). The SCBA trial took longer than the LC trial (p = .046). Heart rate and lactate measures were not different between trials. RPE was higher in the SCBA trial (6.7 ± 1.7) and LC (6.3 ± 1.5) compared to the PT trial (4.6 ± 1.8; p<.001). CONCLUSION: Load carriage and the respirator elicit a large decrement in occupational performance. Performance in PT clothes is not an accurate depiction of performance in load carriage. Firefighters and practitioners must identify safe and effective training strategies to prepare firefighters for the occupational demands of load carriage and respirator use.

Relationship between novel design modifications and heat stress relief in structural firefighters’ protective clothing

The purpose of this study was to investigate design modifications in structural firefighter turnout suits for their ability to reduce heat stress during firefighting activities. A secondary aim of this research established a benchmark for the manikin heat loss value necessary to achieve significant improvements in physiological comfort. Eight professional firefighters participated in five simulated exercise sessions wearing a control turnout suit and one of four turnout prototypes: Single Layer, Vented, Stretch, and Revolutionary. Physiological responses (internal core body temperature, skin temperature, physiological strain, heart rate, and sweat loss) were measured when wearing each turnout suit prototype. Results demonstrated a significant increase in work time and significant reductions in heat stress (core temperature, skin temperature, and physiological strain) when participants wore the Single Layer, Vented, and Revolutionary prototypes. An estimated garment heat loss value of 150 W/m2 was determined in order to achieve a significant reduction in heat stress.

Functional Design and Evaluation of Structural Firefighter Turnout Suits for Improved Thermal Comfort

Structural firefighter prototype designs incorporating ventilation, stretch, and modularity were developed following Watkins’ functional design process. Prototypes were designed and manufactured, including single-layer, vented, stretch, and combination prototypes. Prototype garments were evaluated for improved thermal comfort and heat loss using sweating thermal manikin assessments in two conditions: static (standing still with no wind) and dynamic (walking with wind). Raw thermal and evaporative resistance data from the manikin testing were input into a thermal modeling software system (RadTherm®) and physiological responses (core temperature, skin temperature, and sweat rate) were predicted for each prototype. A significant improvement in heat loss was measured when ventilation openings and modularity were added to the design of the clothing system. The single-layer, vented, and combination prototypes also had significantly lower increases in predicted physiological responses.

Impact of reinforcements on heat stress in structural firefighter turnout suits

The purpose of this research was to determine the impact of additional textile layer reinforcements on garment heat loss and the physiological comfort of the firefighter. Four structural firefighter turnouts with varying levels of ‘bulk’ were assessed. A base composite analysis was conducted and each suit was evaluated for thermal resistance, evaporative resistance, and overall total heat loss (THL) on a sweating thermal manikin. Raw resistance data were then modeled to predict the physiological responses of firefighters for each turnout suit. Base composite percentages were compared to the heat loss values and predicted physiological responses. The Light Weight suit along with the Control, demonstrated the greatest heat loss values and lowest rise in predicted core temperature. Overall, results depicted the harmful impact that bulky reinforcements may have on wearer physiological comfort as the Heavy Duty suit had significantly lower heat loss and a potentially fatal maximum predicted core temperature.

Contributing factors to structural firefighter injury

Contributing factors to structural firefighter injury

Effect of Self-Contained Breathing Apparatus (SCBA) on Heat Loss in Structural Firefighter Turnout Suits

The purpose of this research was to determine the effect of firefighter's self-contained breathing apparatus (SCBA) on heat loss through clothing ventilation openings in structural firefighter turnout suits. Passive and active ventilation openings were fabricated into structural turnout suits and tested with and without the SCBA to determine the effect on clothing ventilation. Turnout suits were evaluated under two test conditions on a sweating manikin to measure thermal and evaporative resistance. A predicted total heat loss (THL) value was calculated for each suit and compared to a control turnout without ventilation openings. A significant improvement in heat loss was measured when the SCBA harness, mask, and thermal hood were removed from the structural ensemble. Results showed the SCBA harness significantly decreased heat loss in firefighter turnouts.

Analysis of air gap volume in structural firefighter turnout suit constructions in relation to heat loss

Air layers in multi-layer firefighter clothing ensembles resist heat transfer from the body to the environment. By reducing the volume of air between clothing layers, heat loss may be improved throughout the multi-layer firefighter turnout suit clothing system, potentially leading to reduced heat strain for the wearer. This research utilized a systems-level approach to the methodology in order to measure the effects of fabric properties and garment air gap dimensions on clothing system heat loss through specially configured turnout suit constructions. One experimental configuration incorporated a tight fitting stretchable moisture barrier garment. Another construction used thermal knit underwear to represent a closer fitting thermal liner. Air gap surface area, volume, and thickness were estimated using three-dimensional body scanning. This study showed the significant impact of fabric air permeability and clothing air gap volume on heat loss through structural firefighter suits. Tested individually, the tighter fitting moisture barrier construction permitted greater heat loss in comparison to the traditional fit moisture barrier. Heat loss differences associated with moisture barrier fit were not observed when the moisture barriers were configured in the three-layer turnout clothing system. This research showed that microclimate air gap volume is strongly correlated with total heat loss. It confirmed the significant impact of clothing air layers on heat loss through firefighter turnout systems.