5.1 Firefighters are routinely exposed to radiant heat in the course of their fireground activities. In some cases, firefighters have reported burn injuries under clothing where there is no evidence of damage to the exterior or interior layers of the firefighter protective clothing.5 Low levels of transmitted radiant energy alone, or a combination of the transmitted radiant energy and stored energy released through compression, can be sufficient to cause these types of injuries. This test method was designed to measure both the transmitted and stored energy in firefighter protective clothing material systems under a specific set of laboratory exposure conditions.

5.2 The intensity of radiant heat exposure used in this test method was chosen to be an approximate midpoint representative of ordinary fireground conditions as defined for structural firefighting (1, 2).6 The specific radiant heat exposure was selected at 8.5 ± 0.5 kW/m² (0.20 ± 0.012 cal/cm²-s), since this level of radiant heat can be maintained by the test equipment and produces little or no damage to most NFPA 1971-compliant protective clothing systems.

5.2.1 Utech (2) defined ordinary fireground conditions as having air temperatures ranging from 60 to 300 °C and having heat flux values ranging from 2.1 to 21.0 kW/m² (0.05 to 0.5 cal/cm²-s).

5.3 Protective clothing systems include the materials used in the composite structure. These include the outer shell, moisture barrier, and thermal barrier. It is possible that they will also include other materials used on firefighter protective clothing such as reinforcement layers, seams, pockets, flaps, hook and loop, straps, or reflective trim.

5.4 The transmission and storage of heat energy in firefighter protective clothing is affected by several factors. These include the effects of wear and use conditions of the protective clothing system. In this test method, conditioning procedures are provided for the laundering of composite samples prior to testing, and also composite sample moisture preconditioning. The amount of moisture added during preconditioning typically falls into a worst-case amount in terms of predicted heat transfer, as suggested by Barker (3).

5.5 Two different procedures for conducting the test are provided in this test method. Procedure A measures only the transmitted energy that passes through the composite, without compression, during the exposure time. In this approach, the length of the radiant exposure is likely to be sufficient in the prediction of a second-degree burn injury. Procedure B involves using a fixed radiant heat exposure time to determine if a second-degree burn injury will or will not be predicted. If a second-degree burn injury is predicted, the time to a second-degree burn injury is reported. If a second-degree burn injury is not predicted, the result is indicated as “no predicted burn.” This procedure includes recommended fixed radiant exposure times.

1.1 This test method uses one of two procedures to measure: (1) heat energy, which can be directly transmitted through the multilayer structure without compressive force, that can result in predicted burn injury, or (2) heat energy directly transmitted through the multilayer structure, followed by applying a compressive force, which rapidly releases stored heat energy in the multilayer structure that can result in a predicted burn injury.

1.1.1 This test method is applicable only to protective clothing systems that are suitable for exposure to heat and flames.

1.1.2 Flame resistance of the material system shall be determined prior to testing according to the applicable performance or specification standard, or both, for the material’s end use.

1.2 This test method establishes procedures for moisture preconditioning of firefighter protective clothing material systems.

1.3 The second-degree burn injury prediction used in this standard is based on a limited number of experiments on forearms of human subjects.

1.3.1 The length of exposures needed to generate a second-degree burn injury in this test method exceeds the exposure times found in the limited number of experiments on human forearms.

1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are mathematical conversions to English units or other units commonly used for thermal testing.

1.5 This standard is used to measure and describe the properties of materials, products, or assemblies in response to radiant heat under controlled laboratory conditions but does not by itself incorporate all factors required for fire hazard or fire risk assessment of the materials, products, or assemblies under actual fire conditions.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific precautionary information is found in Section 7.

1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.