UNE-EN ISO 6942:2022

Heat transfer levels:

Time t12: time in seconds, expressed with one decimal, to obtain an increase in calorimeter temperature of (12  0.1) ºC.

Time t24: time in seconds, expressed with one decimal, to obtain an increase in calorimeter temperature of (24  0.2) ºC.

Thermal transmittance (TF): A measure of the fraction of heat transmitted through the specimen when exposed to a radiant heat source. It is numerically equal to the ratio of the transmitted and incident heat flux densities.

• TYPE A: A specimen is clamped to a vertical frame and exposed to a specified level of radiant heat for a specified time.
  The level of radiant heat is set by adjusting the distance between the sample and the source of heat radiation. After exposure is complete, the sample and its individual layers are examined for any visible changes.
  After irradiation, the sample or the individual layers of the multilayer assembly are inspected. Note, for the sample or for each individual layer of the multi-layered assembly, any changes (eg, discoloration, scaling, charring, breaking, melting, shrinking, sublimation, etc.) observed.

• TYPE B: A specimen is attached to a vertical frame (sample holder) and exposed to a given level of radiant heat. The times required to obtain a temperature rise in the calorimeter of 12 ºC and 24 ºC are determined and expressed as radiant heat transfer rates.
  One side of the test socket is attached to one of the side plates of sample holder B, and the sample is held in contact with the surface of the calorimeter, by applying a force of 2 N. test is withdrawn. and the start of irradiation is recorded. The mobile screen closes when a temperature rise of approximately 30ºC is reached.
  The times t12 and t24, expressed in seconds with one decimal, are determined to obtain an increase in calorimeter temperature of (12 ± 0.1) ºC or (24 ± 0.2) ºC, respectively. As required by the specific standard, the result of the difference between t24 and t12 is calculated and noted.

TF (technical transition) Q0 and RHTI12 and RHTI24 are determined, measure of time t12 or t24 expressed in 0.1s for the increase in temperature of the calorimeter of 12ºC or 24ºC respectively. The radiant heat transfer index, RHTI24-RHTI12 (Q0) for the incident heat flux density is determined RHTI24 minus RHTI12.

For both methods the following is used:

– Radiant heat source

– Test frame

– Sample support

Added for method B:

– Calorimeter

– Temperature measurement and recording device

The radiant heat source consists of 5 SiC heating rods with an electrical resistance of 3.6 Ω ± 10% at 1070ºC.

The heat flux density:

– Low levels: 5kW/m² to 10 kW/m²

– Medium levels: 20 kW/m² to 40 kW/m²

– High levels: 80 kW/m²

Essential calibration of the radiant heat source prior to the test.

For tests carried out by method A, one sample must be used and for those carried out by method B, at least three samples must be used for each level of heat flux. If the material to be tested is not very homogeneous, at least three samples should be tested by method A and five by method B.

Samples should have dimensions of 230 mm X 80 mm.

The composite samples should reproduce the multi-layer clothing ensembles as they are used in practice. If the supplier of the material does not indicate which is the external surface, the tests must be carried out on both sides.

Test conditions: room temperature between 15-35ºC and the calorimeter has to be cooled to room temperature ±2ºC before each test.

– Make reference to the ISO 6942 standard

– Description of the test material (commercial name, fabric face, color, layers…)

– Temperature and Humidity of the test atmosphere

– Number of samples tested

– Method A: skin change description

– Individual values ​​Q0, TF, t12, t24, RHTI12, RHTI24 and RHTI24-RHTI12