Limits of and possibilities to improve the IREQ cold stress model (ISO/TR 11079). A validation study in the field

Estimated insulation (Icl) of clothing worn by workers daily exposed to air temperatures between 0 and 15 degrees C was compared with the corresponding insulation calculated for thermal neutrality using the IREQ-model (IREQneutral, ISO/TR 11079). The goal was to determine possible limitations of the applicability of the IREQ-model and to stress to necessities and possibilities to improve the model. Sixteen female and 59 male workers (16-56 yr) were monitored during their work. According to their cold stress at the workplace they were allocated to three groups (33 persons were exposed to constant temperatures of more than 10 degrees C, 32 to less than 10 degrees C, and 10 persons experienced frequent temperature changes of 13 degrees C. Another categorization concerned workload (8 persons worked at metabolic rates of less than 100 W/m2, 50 persons worked at 101-164 W/m2, and 17 worked at more than 165 W/m2, respectively). The analysis of the differences between estimated worn insulation (Icl) and calculated IREQneutral revealed that the IREQ-model applies for air temperatures up to 15 degrees C and for temperature changes of 13 degrees C (at least) but needs to be improved with respect to gender. The IREQ model does not apply sufficiently for high and largely varying workloads (165 W/m2 and more). However, these situations are beyond the currently available possibilities to protect workers adequately with conventional clothing material. A suitable short-term measure is a more even work flow by avoiding activities with very high and low metabolic rates.