That depends on the kind of hybrid you get, as there are a lot of different certificates mattress manufacturers can apply for. Hybrids with memory foam may come with a CertiPUR-US certification to indicate the memory foam is low in toxic chemicals. Meanwhile, if you get an organic latex hybrid, look for a GOLS (Global Organic Latex Standard) certification to indicate pure organic latex. Mattresses that use other textiles like cotton or wool fibers in their cover or components can apply for a GOTS (Global Organic Textile Standard) certification to indicate their status as organic, non-toxic, and sustainable. A GreenGuard Gold certification indicates the hybrid has low VOC emissions. While an OEKO-TEX Standard 100 certification indicates the whole mattress is free of toxic chemicals, whereas a CertiPUR-US, GOLS, or GOTS certification would only apply to the relevant textile and foam components of the mattress.