What is BS 5608 - Specification for preformed rigid polyurethane (PUR) and polyisocyanurate (PIR) foams about?  
BS 5608 specifies the composition, physical properties, and dimensional tolerances for preformed rigid polyurethane (PUR) and polyisocyanurate (PIR) foams for the thermal insulation of pipework and equipment.
BS 5608 applies to slabs, cut and molded pipe sections, and radiused and beveled lags. The nominal temperature range for which the insulation material is suitable is – 180 °C to + 140 °C (see Annex F).
NOTE 1 No values are specified in this standard for the length, bore and outside diameter of pipe sections and lags or for the length and width of slab stock; these should be as specified by the purchaser.
Who is BS 5608- Specification for preformed rigid polyurethane (PUR) and polyisocyanurate (PIR) foams for?  
BS 5608 on specifications for thermal insulation is for:
- Foam manufacturers and suppliers   
- manufacturers and suppliers   of thermal insulations
- Test providers for thermal insulation
Why should you use BS 5608 - Specification for preformed rigid polyurethane (PUR) and polyisocyanurate (PIR) foams? 
Polyisocyanurate foam (PIR), also referred to as PIR is a closed cell thermoset polymer formed by reacting a di- or Poly isocyanate with a polyol. The thermal conductivity can be lower than that of polyurethane foam.
BS 5608 provides specifications and requirements for PUR and PIR foams for thermal insulation of pipework and equipment.
BS 5608 provides you with general specifications and requirements for different tests of insulation that help you to check whether they will withstand variable temperatures. 
The test methodologies given in BS 5608 enable you to examine the thermal insulation for any signs of deformation or delamination of reinforcement or lining, which contributes a lot to maintaining the high quality and efficient functioning of PIR and PUR foam. 
