NASA is seeking effective flame retardant (FR) treatment for next-to-the-skin crew clothing. This treatment must be compatible with fabrics relevant to the NASA space crew. The treated clothing must remain: (1) nontoxic even under flame, (2) comfortably wearable, (3) durable to withstand multiple washing/drying cycles, and (4) resistant to combustion in an atmosphere of 36% oxygen at a pressure of 8.2 psi (56.5 kPa). Currently, there exists a technology gap to meet FR needs for crew clothing. Toward this, InnoSense LLC (ISL) will continue developing durable FR treatment using non-halogenated and nontoxic organophosphorus materials (FROM). In Phase I, ISL demonstrated the technical feasibility by achieving permanent FR coating for polyester (PET) fabrics. Test data showed high coating durability, soft-to-the-touch attribute, nontoxicity, insignificant weight gain, limited oxygen index of ?56%, and excellent FR performance in both 20% and 36% O2 environments, thereby, exceeding Phase I performance targets. In Phase II, ISL will focus on the optimization and scale-up of treatment process, and perform rigorous testing. Evaluation and validation of FROM-treated fabric in a simulated space environment are also planned. At the end of Phase II, FROM-treated prototype fabric samples will be delivered to NASA for evaluation. Potential NASA Applications (Limit 1500 characters, approximately 150 words): FROM-treated fabric technology can be used for current or future NASA crew clothing. Other NASA uses are in protective clothing, curtains, drapes, upholstery, bedding, carpets, tents, etc. This technology will also benefit several space programs, particularly the lunar Human Landing System, Orion, Gateway, and Artemis, enabling the astronauts to function in habitats, pressurized rovers, and other space vehicles with enriched oxygen atmospheres and to shorten pre-breathe times prior to extravehicular activities. Potential Non-NASA Applications (Limit 1500 characters, approximately 150 words): FROM-treated fabrics can be used for firefighters, electrical workers, foundry workers, and military personnel. The treatment can be used for protective clothing, blankets, tents, furniture, and mattresses. This technology will also have applications for paper (e.g., stocks, bonds, wills, etc.), coatings or fillers for structural and electrical components. Duration: 24