The thermal resistance of the Republic of Latvia state administrative employees’ functional daily clothing basic set layering has been determined with the aim to predict the wearer’s level of physiological comfort, body cooling or possible heat stroke wearing particular clothing in its guaranteed period of use. For the study by means of a thermal manikin according to ISO 15831 experimental functional daily clothing sets of the Ministry of Interior of the Latvian Republic institutions were chosen – four of the State Police and State Border Guard. It was found that the studied clothing sets correspond to a great extent to the officers’ specific job assignments and the winter, spring, summer and autumn seasons of the climatic conditions of Latvia. The factors causing body cooling or heat stroke have been identified which may pose a threat to the officer’s health and life during performance of his/her job duties. For evaluation of the experiment’s results and the prediction of the clothing functionality the calculation methods of ISO 11079 and ISO 7933 have been used.