The standard for hardwood flooring adhesives in the U.S. is polyurethane.
Though it is high quality in its ability to firmly adhere and restrict movement in hardwood flooring, it is relatively high in V.O.C. emissions.(the Volatile Organic Compounds that off-gas over a period of time. These emissions are often associated with “Sick Building Syndrome” and its related negative impact on the health of the human and animal occupants. One of the most well known of these adhesives is Bostik Best. 

The more advanced European standard is Modified Silane Adhesives.
This class of hardwood adhesive is a better choice than traditional polyurethane adhesives in that they contain no Isocyonates , Diisocyanates, nor solvents. Unfortunately, this class of product still emits considerable quantities of the toxic v.o.c. methanol.  They also are catalyzed by heavymetals, which are labeled as a health risk in more environmentally advanced Europe.

The new European Green Standard is called Next Generation Silane Modified Adhesive. It is the only adhesive that emits zero harmful V.O.C.s, and contains no dangerous heavy metal catalysts nor solvents.   Though various other manufacturers in the States are starting to introduce polyurethane and Silicone Modified adhesives lower in v.o.c.s than previously available in their class, they are of the old technology that is far surpassed by the new Next Generation Silane Modified patented technology. This clean new product is available for all Zumaya installed projects.  It is also available for sale to all Zumaya Customers who utilize their own installation crews