The most crucial function of a garment is to protect the human body from primary outer influences such as wind, rain, sunlight, dust, and mechanical influences. Protective clothing protects individuals exposed to life-threatening or hazardous environments during work. Aerial application ranks high-risk because pilots perform their tasks under drastic working conditions. This is why their clothing should protect against extreme conditions such as high temperature and flame, rain, aggressive and reactive chemicals, hazardous chemicals, etc.
The National Center for Biotechnology Information tested fire-resistant clothing by focusing on the most commonly used body positions (standing, squatting, or sitting) and extreme movements when wearing clothing and performing a job. The following is a summary of their findings.
Essential Functions and Design Considerations
Protective clothing protects individuals from environmental factors like wind, rain, sunlight, dust, and mechanical influences. For professionals in hazardous fields, such as firefighting, the clothing must offer robust protection against extreme conditions, including high temperatures, flames, water, cold, and dangerous chemicals. The design must also accommodate various body positions and movements, such as standing, squatting, and sitting in a cockpit environment.
Creating adequate protective clothing against heat and flame requires a collaborative effort involving designers, engineers, pilots and firefighters. The comprehensive design process covers developing high-tech products from initial concept through feasibility analysis, material selection, prototyping, and manufacturing. Integrating smart technologies with textiles enhances the functionality of protective clothing, necessitating multidisciplinary collaboration among engineers, fashion designers, and scientists.
Advances in Fire-Resistant Materials
Significant advancements have been made in fire-resistant fibers, high-performance fibers with unique properties, and microporous materials. These innovations extend the life of protective clothing and improve its care while ensuring adequate protection. Various evaluation methods, including thermal manikin tests and hot plate tests under specific conditions, have been established to assess the effectiveness of these materials. Continuous research in textile technology, physiology, ergonomics, and functional design is pivotal in enhancing the durability, moisture transfer, and thermal stress management of protective clothing.
Material Selection
Firefighting gear and fire-resistant flight suits typically incorporate fire-resistant materials such as aramid fibers (e.g., Nomex®), modacrylic fibers, cotton fibers, or textiles treated with flame-retardant finishes. These materials are often blended to enhance comfort and transport moisture and heat. High thermal protection, as in fire turnout gear, is achieved through multilayer or thick textile materials, with each layer contributing significantly to the overall level of protection. For clothing in an aviation application, flight suits are made from aramid fibers such as Nomex®, modacrylic fibers, cotton fibers, or other textile materials with a flame retardant finish to achieve better comfort, which includes the transport of moisture and heat. This is extremely important for comfort when using clothing systems in various activities, including extreme conditions. Recently, different techniques for characterizing fire-resistant textile materials have been conducted.
So far, new types of fire resistance fibers, high-performance fibers of unique properties, and microporous materials have been developed, which provide for the long life and easy care of protective clothing as well as, at the same time, providing the user with an adequate level of protection and safety. Special procedures of evaluating the characteristics of protective materials, tests with a thermal manikin and hot plates for the determination of fabric and clothing characteristics under special conditions have been developed. Scientists from different fields (textile technology, physiology, ergonomics, functional design, etc.) are continually working on research such as the development and production of protective clothing and materials, study of their durability during use testing by volunteers in simulated environmental conditions, research on moisture transfer through clothing and thermal stress, and how to design and implement the appropriate test methods.
Researching Flammability Protection
A paper developed by the National Center for Biotechnology Information investigated the flammability properties of the clothing system for protection against heat and flame and analyzed the damage caused to clothing. A clothing system consisting of underwear comprises 70% wool fiber and 30% modacrylic fiber and overalls for protection against heat and flame, made of 55% modacrylic fiber and 45% cotton fiber, much like an aviator’s flight suit.
Results
By testing with a fire manikin and an explosive fire simulator, data on the degree of burns in the case of using a clothing system (underwear and overalls) that was exposed to an explosive flame for 4 seconds were obtained.
The clothing system consisting of underwear and single-layer overalls intended for firefighters to extinguish open fires after exposure to explosive fire for 4 seconds was found to have minor damage. Visual assessment of the damage to the clothing system was performed for 116 seconds after the flame was extinguished in the chamber where the fire manikin test was performed. Based on the observations, it was established that there was no damage to the underwear. There was minor damage to the overalls on the tops of the pockets and the sleeves and part of the trousers below the knee. The visual assessment revealed that there was a shrinkage of material on certain parts of the overalls (shoulder area) and a partial change in color on the material of the overalls (dark brown and black) caused by fire (visible on the folds on the overalls, which appeared during the test.
Damage to the clothing system confirmed the results obtained by the computer display of test results on the fire manikin and microscopic analyses, which did not show damage to the structure. The results of the fire manikin showed that after 17 seconds, the first appearance of first-degree burns was 1% of the total area of human skin in the left forearm. Second-degree burns occurred on the head but were not considered because the test was performed without head protection (without the use of a helmet and undercap). Four sensors indicating third-degree burns were identified as invalid because during the calibration of the fire manikin itself, before the test, it was found that the sensors were out of order. Results from fire manikin and damage to the clothing system showed that the user, exposed to fire and heat, would not have injuries dangerous to health and life, thus showing that the clothing system met the expected properties of use/protection.
If the user used such a clothing system exposed to direct fire for 4 seconds, they would survive without significant health problems. Still, they should immediately move away from further heat and flame exposure.
For the research, an analysis of the primary material from which the overalls were made and an analysis of the material after flame exposure during the fire manikin test were made. The primary material was made from 55% modacrylic fiber and 45% cotton fiber with a built-in antistatic grid, mass per unit area 295 g/m2, woven in canvas. The breaking force in the warp direction was 1049 N and 808 N in the weft direction. After exposing the overalls to explosive fire during the test on the fire manikin and visual assessment of the damage, sampling of parts of the overalls in the direction of the warp and weft was performed.
Based on theory and conducted research, except for the critical factor of material selection, great attention should be paid to the functional design of clothing for protection against heat and flame. The tested clothing system provides a high degree of protection, partly due to the adequate use of fire-resistant underwear. The results of testing using the fire manikin showed that when using such a clothing system, the user would not suffer tissue damage, which could pose a danger to health or life if the users are immediately removed from the fire and heat.
If the user continues to use a clothing system exposed to explosive fire, the clothing system will not provide adequate protection due to the damage. Without fire-resistant underwear, the user would obtain burns in more areas than fire-resistant underwear, mainly if they used ordinary cotton underwear, which absorbs moisture faster. The user would “be cooked “when exposed to high temperatures. If the user were exposed to prolonged fire, the damage to the overalls and injuries would be more significant.
Research with the help of a fire manikin and an explosive fire simulator dramatically helps us to predict the degree of burns of users of the clothing systems and the possibility of survival. Such research is fundamental in the first phase of designing clothing systems, which should protect against heat and flame. All of the materials used must be fireproof so that the failure does not further endanger the health or life of users. In the design and production processes of protective clothing systems, the cooperation of experts in materials and fibers, designers, constructors, technologists, and end users and manufacturers of protective clothing is necessary.
This research underscores the importance of material selection and functional design in developing practical protective clothing against heat and flame. The tested clothing system demonstrated high levels of protection, particularly with fire-resistant underwear. However, the protective properties of the clothing diminish after exposure to fire, emphasizing the need for ongoing improvements.
Collaborative efforts among material scientists, designers, engineers, and end-users are essential in designing and producing effective protective clothing systems. The study highlights the necessity of using fireproof materials and advanced testing methods to ensure user safety in hazardous environments.
The TG-IR and MCC results suggest that while the protective clothing system shows good initial stability against heat, further development is needed to improve its overall thermal resistance. Continuous innovation and rigorous testing are vital to enhancing the performance and safety of protective clothing for individuals working in high-risk environments.
