Gas tight suits are typically made from multi-layer laminate fabrics or high-performance elastomers like Viton, Butyl rubber, or PVC. You should request a Chemical Permeation Data Sheet from the supplier, which lists the 'breakthrough time' for specific chemicals. For high-risk environments, look for materials that offer at least 480 minutes of protection against a broad spectrum of industrial chemicals and CBRN agents. Ensure the integrated visor is made of anti-fog, impact-resistant materials like Teflon-coated polycarbonate.