On the modern battlefield, protection from the enemy surveillance is vital for the survivability of the force. The beginning of the XXI century has made surveillance by means of thermal devices an advanced solution to the searching, identification and recognition of heat sources, including even people. The research has been made in order to define the protection level of the Combat Individual Protection System (CIPS) of the Latvian Army from the thermal infrared (TIR) detectors. Eleven different CIPS combinations have been used in the weather conditions of the experiment. The methodology of the field evaluation has been established, and special design clothing system for the sniper and recon units as well as for the camouflage in the snowy terrain has been identified based on the best TIR protection quality. Implementation of the CIPS-Mod1- SNIPER/RECON-system into CIPS has been suggested. The developed field trial methodology of the TIR protection quality definition can be applied to further research on the visual (VIS) and near infrared (NIR) quality of the combat clothing systems.