One of the most important challenges for thermoplastic polymers is to find flame retardants (FRs) capable of efficiently protecting them. At the same time, these desired FRs should be environmentally sustainable, cheap, and suitable for most of the polymers employed on the industrial scale. Obviously, it is almost impossible to design such a universal FR to be used for polymers having different chemical structures. We have recently demonstrated the efficiency of a deoxyribose nucleic acid (DNA) coating as a FR solution for cellulose and ethylene-vinyl-acetate (EVA) copolymer. Pursuing this research, in the present study we investigate the FR effect of different DNA amounts on 3 mm EVA samples in order to optimize its cost/effectiveness ratio. FR performances were evaluated with a cone calorimeter under 35 and 50 kW/m2. Then, the optimized DNA amount was tested on EVA samples having different thicknesses (namely, 1 and 6 mm) in order to establish whether a correlation between DNA amount and sample mass exists. Finally, the DNA potentialities as "universal" FR have been investigated on samples of polypropylene (PP), acrylonitrile-butadiene-styrene (ABS), polyethyleneterephthalate (PET), and polyamide 6 (PA6) and compared with some of the best FR solutions found in the literature or on the market.