Formulated Materials® APS is a Low VOC acrylic primer and sealer that improves the performance of fire-rated underlayments and self-levelers by providing a solid bond to the substrate during installation and increases moisture and abrasion resistance and durability of underlayments and levelers when applied to fully cured surfaces. APS is easy to use and is appropriate for use with both porous and non-porous substrates when applied as a primer