Conductive and Compressive Heat Resistance (CCHR)A new Conductive and Compressive Heat resistance (CCHR) test was added to the 2000 edition of NFPA 1971 Standard to specify minimums in protective insulation required in high compression areas.
The requirement is that the CCHR rating of shoulder and knee areas, when compressed, must equal the established base garment rating. This is intended to ensure that the shoulder and knee areas will provide the same level of protection when compressed, as does the remainder of the garment. The test is run in both the wet and dry conditions.
The CCHR rating is the time in seconds to achieve a temperature rise of 24° C. The minimum requirement established in the 2000 edition was 13.5 seconds, which was arrived at by testing a garment with a TPP of 35 on a hot plate set at 280°C, under a pressure of 1/2 lb. per square inch. The shoulder area is tested under 2 lbs. psi, which simulates a firefighter wearing a 2" SCBA strap, with a 40 lb. fully loaded tank. The knee section is tested at 8 lbs. psi, which represents the amount of force that a 180 lb. firefighter would exert to the knee area when in the kneeling position. in the 2007 edition of NFPA 1971, the CCHR requirement increased to 25 seconds.
The original requirement did necessitate additional insulation in some systems, depending upon which materials the base garment was built from. However, Globe made the decision to automatically add a second layer of thermal liner in these high compression areas, to ensure that minimum requirements were always exceeded. Our shoulder reinforcements extend 5" from the top of the shoulder in the front and a full 7" in the back. For the knee area, we install not just a layer of thermal liner, but also an additional layer of moisture barrier, for a level of protection far and above the minimum requirement.