Not unlike other intumescents, sodium silicate, both in bead form and in liquid form, are inherently endothermic, due to liquid water in the water glass and hydrates in the prill form. The absence in the US of mandatory aging tests, whereby PFP systems are made to undergo system performance tests "after" the aging and humidity exposures, are at the root of the continued availability, in North America, of PFP products that can become inoperable within weeks of installation. Indiscriminate use of sodium silicates without proper waterproofing measures are contributors to the problems and risk. When sodium silicates are adequately protected, they function extremely well and reliably for long periods. Evidence of this can be seen in the many DIBt approvals for plastic pipe firestop devices using Palusol (a product of BASF), which use waterproofed sodium silicate sheets.