In automobile manufacturing plants, electric arcs generated during welding, thermal cutting and heat treatment release high-intensity optical radiation, including infrared thermal radiation, ultraviolet radiation and strong visible light. Beyond defending against welding spatter and brief open flame, the core task of the Automotive Industry Fire Suit is to reflect, attenuate and block various radiant energy emitted by electric arcs. Unlike tangible hazards such as molten slag, radiation propagates through air in the form of electromagnetic waves without physical contact. Even without direct contact between hot objects and the human body, radiation can cause skin burns and photochemical damage. In many workplace safety incidents, skin erythema, peeling and burns on welders are not caused by flame or molten droplets, but by prolonged exposure to arc radiation. Understanding radiation types, propagation rules and the suit’s protective mechanism against radiation is critical for proper application of this protective equipment.

　　Radiation emitted by electric arcs falls into three main categories: infrared thermal radiation, ultraviolet radiation and intense visible light. Among them, infrared radiation serves as the primary source of thermal injury. These long-wave electromagnetic waves are invisible to human eyes and produce an immediate burning sensation on human skin. When infrared radiation hits ordinary fabric, most energy is absorbed by fibers, rapidly raising fabric temperature and transferring heat inward continuously, which eventually leads to thermal burns on skin. Ultraviolet radiation comes from short-wave bands of electric arcs, including UVA, UVB and UVC. It carries strong photochemical effects and may not trigger immediate burning pain, yet short exposure causes electric photodermatitis with skin redness and peeling. Long-term cumulative exposure also damages the eye lens. Intense visible strong light does not create direct high-temperature burns, yet severe glare impairs visual judgment and indirectly triggers safety accidents. These three types of radiation superimpose and emit simultaneously. Therefore the radiation protection design of the fire suit must comprehensively attenuate infrared, ultraviolet and visible light at the same time.

　　The first defensive line of the fire suit against radiation is the low-absorption, high-reflection modified layer on the fabric surface. Conventional flame-retardant fabrics only resist combustion and cannot reflect radiant energy effectively. Most infrared energy will be absorbed by textile fibers. After weaving, the outer fabric of this fire suit undergoes surface functional modification to build a low-surface-energy reflective protective film. When arc radiation strikes the garment surface, part of the infrared radiation is reflected back to the surrounding environment instead of being absorbed by fibers, reducing the radiant heat flux received by the fabric at the source. The performance of the reflective coating directly determines radiation protection capacity. Once the coating is worn, scratched or ablated, reflection efficiency drops sharply, massive infrared radiation is absorbed by fabric, and radiation protection fails. For this reason, the integrity and thickness of the protective coating on fabric surfaces of high-radiation exposed zones such as chest, shoulders and upper arms are key inspection items.

　　Fiber selection of the fabric substrate forms the second barrier for radiation protection. The suit substrate adopts meta-aramid blended inherently flame-retardant fibers. Such aramid fibers will not rapidly age and embrittle under strong radiation exposure, and their tensile strength will not drop drastically under prolonged ultraviolet irradiation. When radiant energy that cannot be fully reflected by the outer layer penetrates the surface layer, the dense textile structure composed of aramid fibers scatters and absorbs electromagnetic waves to attenuate and block further inward penetration of radiation. The fabric adopts high-density twill weaving with tightly interwoven yarns to reduce channels for electromagnetic waves to penetrate fabric pores. Excessively large pores allow arc radiation to pass directly through gaps and reach the skin; overly compact fabric prevents outward discharge of sweat vapor generated by human bodies, causing internal heat accumulation inside the garment and aggravating heat stress. Fabric weave density must be repeatedly adjusted to balance radiation blocking and breathable heat dissipation.

　　A multi-layer composite structure further extends the time required for radiation penetration. The fire suit adopts a three-layer composite system. The outer layer reflects radiation; the middle barrier film absorbs residual ultraviolet and infrared bands and blocks hot airflow accompanying radiation; the fluffy inner aramid insulation felt uses trapped static air inside to delay inward conduction of heat converted from radiation. After radiant energy is absorbed by fabric, it converts into thermal energy and stores inside the textile, creating a heat accumulation effect. Even when welders temporarily move away from welding torches, radiant heat trapped inside fabric continues releasing toward the human body and causes delayed burns. The purpose of multi-layer construction is to extend the time window for radiant energy conversion and heat conduction and reserve safety evacuation time for operators. The suit adopts a zoned structure: full three-layer composite fabric is used on high-radiation areas including chest, shoulders and upper arms to strengthen radiation attenuation. Lightweight double-layer fabric is applied at armpits, waist sides and elbow joints to retain basic radiation protection while reducing weight and preserving flexibility for welders to lift arms and turn bodies during operation.

　　Radiation protection performance tests quantify the garment’s ability to attenuate electromagnetic radiation. Test items include infrared radiant heat flux test, ultraviolet transmittance test and thermal protective performance test. The infrared radiation test simulates infrared energy from welding arcs, measures fabric surface reflectivity and calculates heat flux penetrating fabric toward simulated skin. The ultraviolet transmittance test examines the fabric’s blocking efficiency for ultraviolet bands. Qualified finished garments must maintain extremely low ultraviolet transmittance and block most arc ultraviolet radiation. Cyclic aging experiments are also carried out during testing to simulate workshop radiation exposure, washing and abrasion repeatedly, and inspect the degradation rate of radiation protection indicators after multiple uses. Once the fabric surface coating is scratched, fibers carbonize or inner layers compress, the fabric’s reflection and attenuation capacity decline. If test indicators exceed limits, radiation protection is judged invalid.

　　In field application, many factors alter radiation protection performance. Working distance is a key variable. Radiation intensity follows the inverse square law of distance: the closer welders stand to the electric arc, the faster radiant energy multiplies and the radiation load borne by the suit rises sharply. Ambient humidity in workshops also creates impacts. Water vapor adhering to fabric surfaces under high-humidity conditions changes the optical properties of textiles and reduces the reflection efficiency of reflective layers. During wear, the fire suit must be fully fastened with plackets, collars and cuffs fully tightened. An unzipped suit creates gaps acting as penetration channels for radiation, exposing bare skin directly to arc radiation and causing local sunburn-like burns. Continuous working duration must be controlled to avoid continuous accumulation of radiant energy inside fabric. Operators should take breaks in ventilated zones between tasks to release stored heat within the garment.

　　Maintenance directly determines the service life of radiation protection. Only neutral detergent can be used for cleaning. Strong alkali and bleaches are forbidden. Bleaches destroy the fabric surface reflective coating, damage aramid fibers and greatly reduce blocking performance against infrared and ultraviolet radiation. High-temperature drying is prohibited, for high heat accelerates aging and peeling of reflective coatings and compresses inner insulation felt. Each washing cycle causes minor wear of reflective coating. When reaching the maximum laundering lifespan, fire suits must be scrapped and cannot continue to be used for welding work. Storage environments should be shaded and dry, kept away from oil contamination and sharp workpieces to prevent coating scratches. Long-term storage under strong light allows ultraviolet rays to continuously age fabric and surface modified layers and degrade radiation protection performance.

　　Radiation protection has clear application boundaries. The fire suit only handles arc radiation under conventional welding conditions in automotive workshops and cannot withstand extremely intense, prolonged high-level radiation environments. For high-risk operations such as high-current thick-plate welding and overhead welding, besides the fire suit, supplementary personal protective equipment including welding face shields, flame-resistant sleeves and protective aprons must be matched to form full-body radiation protection combinations. The fire suit attenuates rather than completely eliminates radiation. Operators still need to limit exposure duration and cannot work indefinitely in strong radiation environments.

　　In summary, the radiation protection system of the Automotive Industry Fire Suit relies on a surface reflective modified layer, high-density aramid textile and multi-layer composite insulation structure working together to reflect, scatter and attenuate infrared, ultraviolet and visible light radiation generated by electric arcs. Arc radiation in automotive manufacturing workshops is an invisible hazard, and radiation intensity cannot be judged directly by naked eyes. Wear of surface coating and fabric aging will quietly weaken protective capacity. Pre-use inspection, standardized cleaning and timely retirement during daily use are essential to maintain radiation protection performance. Designed specifically for arc radiation hazards at welding stations in automobile workshops, this fire suit builds an electromagnetic radiation barrier in addition to resisting molten slag and flame, lowers risks of photodamage and thermal burns on welders’ skin, and delivers comprehensive high-temperature radiation protection for frontline operators in automobile manufacturing.