Meredith McQuerry

A review of garment ventilation strategies for structural firefighter protective clothing

The purpose of this review article is to evaluate ventilation, within protective clothing, for its benefit towards heat loss. Literature from ventilation studies in the sports apparel, outdoor clothing, military, chemical, and firefighter protection industries will be examined for future research opportunities. Challenges to ventilation such as garment placement, protection, wearability, and durability will be discussed in the context of turnout suits. Ventilation designs will be considered for further evaluation in structural firefighter turnout garments. This article serves as the first comprehensive review of ventilation literature for structural firefighter turnout ensembles. Researchers, technologists, and functional apparel designers may all benefit from such a review. The value of ventilation and its potential contribution to current firefighter turnout research will be discussed.

Evaluating turnout composite layering strategies for reducing thermal burden in structural firefighter protective clothing systems

A modular approach for arranging the component layers used in the construction of structural firefighter turnout garments is explored as a strategy for reducing the thermal burden contributed by these protective garments to firefighter heat stress. An instrumented sweating manikin was used to measure the insulation, evaporative resistance and total heat loss through turnout systems configured to represent different layering strategies. The outer shell, moisture barrier and thermal liner layers of the structural turnout base composite were tested individually to determine each layers thermal insulation and evaporative resistance. Multiple two- and three-layer combinations were analyzed for their application in specific working conditions. This study demonstrates that the moisture barrier layer contributes the most resistance to evaporative heat loss through the turnout system, while dry heat loss is most restricted by the thermal liner component. Removal of a single inner liner layer was equally beneficial for heat loss, regardless of material properties. It shows the potential benefit of turnout design strategy that utilizes a modular or adaptive layering approach to reduce turnout-related heat strain in conditions consistent with fire protection.

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.

Impact of reinforcements on heat stress in structural firefighter turnout suits

Abstract 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.

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.

Validation of a Clothing Heat Transfer Model in Nonisothermal Test Conditions

Heat transfer through clothing systems can mean the difference between life and death for first responders, such as firefighters, who perform intense physical activity in extreme environmental conditions. Total heat loss (THL) is a fabric level test method required by the National Fire Protection Association (NFPA) to assess the thermal burden imposed by materials in the construction of turnout clothing. This methodology, however, does not account for garment fit, construction, or air layers that develop within the clothing. Instead, thermal manikins may be used to measure the THL of entire clothing systems according to ASTM test methods. Environmental test conditions between the two standard methods (fabric versus manikin) differ, creating the need for an adapted heat transfer model for manikin THL comparisons in similar environmental conditions. Therefore, the purpose of this research was to validate the assumptions of a heat transfer model originally developed and published by Ross, Barker, and Deaton (2012) for its accuracy in predicting manikin THL in nonisothermal test conditions. Three protective clothing systems with varying levels of clothing insulation were tested for THL in both isothermal and nonisothermal conditions as well as on the sweating guarded hot plate. Predictive calculations using Ross’s heat transfer model, adapted from the original THL hot plate calculation in ASTM F1868, Standard Test Method for Thermal and Evaporative Resistance of Clothing Materials Using a Sweating Hot Plate, were correlated to the actual manikin measurements taken in isothermal conditions to determine if there is any bias present in the current model.