The purpose of this pilot study is to improve protection of first responders in case of biological disasters (e.g., pandemics, biotoxin incidents). For this goal we will compare two different kinds of personal protective equipment (PPE) to be used for a variety of exercises simulating activities of first responders in the field at two different environmental temperature profiles in a randomized cross-over study design. The goal is to find the best possible compromise between protection and ergonomics as well as to determine potential factors that might limit the performance of first responders while wearing PPE. This should provide guidance for future improvement of PPE and how biosensors for monitoring heart rate and body temperature in combination with AI models may reduce risk for first responders in the field.