Bus, train and aviation seats

Mass transit seats — urban and highway buses, subways and long-distance trains, aircraft and watercraft — use a specialized type of flexible PU foam called CMHR (Combustion Modified High Resilience). Unlike HR foam used in residential furniture and standard automotive, CMHR is formulated with high-efficacy flame retardants to meet strict safety standards in environments where fire represents a critical collective risk.

The standards governing this application are extraordinarily specific: BS 5852 Crib 5 (United Kingdom, dominant in global buses and aviation), FAR 25.853 (civil aviation, fire test for aircraft seats), UIC 564-2 and EN 45545 (European rail), FMVSS 302 adapted and Docket 90 (for American buses), IMO FTP Code (marine). The CMHR formulation meets these standards by adding halogenated or halogen-free flame retardants, additives such as expandable graphite (which expands with heat creating a carbonized barrier), and components that suppress toxic gas emission during combustion.

For even more demanding applications (commercial aircraft, high-speed trains), expandable graphite foam is used — a formulation where graphite particles expand up to 250 times when heated, creating a carbonized insulating layer that protects the foam interior and dramatically retards fire propagation. Typical densities: 40 to 60 kg/m³, with firmness and durability specifications equivalent or superior to automotive HR.