Protective clothing enables humans to operate in adverse environments. However, protective clothing limits heat transfer and hampers task performance due to the increased weight. A good balance has to be achieved between protection on the one hand and human factors aspects on the other hand. In general, the focus is on the protection and consequently human factors aspects are underestimated. Improving ventilation through and under the protective clothing increases sweat efficiency and thus reduces heat strain. Ideally, the sizing of the protective clothing should reflect the human body dimensions. A relatively loose fit enables a wider movement range and better ventilation. In summary, in the selection and evaluation of protective clothing attention should be given to heat strain and fit issues next to the actual protection it offers.