Resilient (vinyl, rubber, linoleuem etc.) flooring over wood sub-floors - most floor covering manufacturers do not approve of the use of a particle board, Oriented Strand Board (OSB), Particle (chip) board or hardboard type underlayment, with the exception of those types rated as "Flooring Underlayment Grade". Wood underlayment products can contain a variety of ingredients such as wax, urea-formaldehyde and isocyanate based adhesives that can cause issues. For this reason, the NFCA Floor Covering Reference Manual states that underlayment panels shall be designated "Underlayment Grade" and be warranted by the panel manufacturer for use under the specified flooring. Underlayment panels shall be free of internal voids, knot holes, splits or cracks and be complete with an upper surface that is sufficiently dense and smooth so that surface grain or texture will not be telegraphed to the surface of any newly installed resilient flooring. Compatibility between underlayment’s, floor covering products and adhesives should be confirmed prior to floor covering installation to avoid issues.