What clo means
Clo is a thermal insulation unit describing the resistance clothing provides to heat exchange. One clo equals 0.155 square metres kelvin per watt. It is used in thermal comfort and cold-exposure models alongside environmental variables and activity characteristics.
An ensemble, not a universal label
An ensemble’s insulation is not necessarily obtained by adding all garment values without corrections. Fit, covered areas and air layers influence it. Interpret a catalogue figure according to the test or reference supporting it. It does not mean anyone can remain indefinitely at a given temperature while wearing that garment.
Wind, movement and moisture
Conditions of use may reduce effective insulation compared with the reference value. Movement and ventilation of the ensemble alter air layers. Moisture can also change performance. Distinguish insulation described under standardised conditions from that corresponding to the assessed situation, applying the corrections specified by the method used.
Relationship with the work
Clothing suitable for standing still may be excessive during intense exertion and promote sweating. When activity subsequently decreases, accumulated moisture can worsen the feeling of cold. Selection must consider the entire work cycle, availability of replacement garments and adjustment options, without interfering with other protective equipment.
A cold-room example
In a hypothetical case, the same ensemble is issued to an order picker and someone waiting beside a door. Their needs are not necessarily identical: activity, draughts and time spent there differ. Assessment compares those conditions with required insulation and also checks hands, feet and freedom of movement.
What to record
The report identifies garments, condition, manner of use and the source of the value applied. Review selection when tasks or conditions change and consider workers’ observations. Clo helps structure thermal assessment; it does not replace certification for protection against other hazards or itself resolve clothing compatibility.
