oil. There is also some work being done on NOPs made from Natural Animal oils. Initially in the US, and since early 2010, it has been routinely possible to replace over 50% of petrochemical-based polyols with NOPs for use in slab foams sold into the mass market, furniture and bedding industries. The commercialised technology also eliminates or greatly reduces the odor problem, mentioned above, normally associated with the use of NOPs. This is particularly important when the NOP is to be used at ever higher percentage levels, to try to reduce dependency on petrochemical materials, and to produce materials for use in the domestic and contract furniture segments which are historically very sensitive to "chemical" odors in the final foam product in people's homes and places of work. Amongst other useful effects of using high levels of Natural Oil Polyols to make foams are the improvements seen in the long-term performance of the foam under humid conditions and also on the flammability of the foams; compared to equivalent foams made without the presence of the NOP. People perspire; and so foams used for the construction of matrasses or furniture will, over time, tend to feel softer and give less support. The perspiration gradually softens the foam. Foams made with high levels of NOPs are much less prone to this problem, so that the useful lifetime of the upholstered product can be extended. The use of high levels of NOP also make it possible to manufacture foams with flame retardants which are permanent, and therefore are not later emitted into the household or work place environment. These relatively recently developed materials can be added at very low levels to NOP foams to pass such well known tests as California Technical Bulletin 117, which is a well-known flammability test for furniture. These permanent flame-retardants are halogen free and key into the foam matrix and are therefore fixed there. An additional effect of using these new, highly efficient, permanent flame retardants, is that the smoke seen during these standard fire tests, may be considerably reduced compared to that produced when testing foams made using non-permanent flame retardant materials, which do not key themselves into the foam structure. More recent work during 2014 with this "Green Chemistry" has shown that foams containing about 50 percent by weight of natural oils can be made which produce far less smoke when involved in fire situations. The