“Clo” is not a girl’s name…

“Clo” is not a girl’s name and in the application I want to discuss, it doesn’t mean Chief Learning officer either.

In this instance it means clothing value and represents the amount of insulation afforded by different clothing in different situations.

Fig 2/20 Insulation values of different kind of clothing (1 clo = 0.155 m²K/W).

This clothing value scale was thought up by the US military in World War 2 to differentiate between the clothing required in the different theatres of war.  Sending an army to the Aleutian islands in tropical gear for example wouldn’t help to promote military efficiency. The equivalent British term, just to be different, is “togs” and one clo is equal to 1.55 togs.

A male will be comfortable ie, at homeostasis, in clothing with the combined insulation of 1 clo where he is sitting in an office with a temperature of 21⁰Celcius and an air speed of 100mms per second at 50% humidity.  This describes your mythical office worker.

Cold store workers, depending on the amount of work they do, require clothing with a clo value of approximately 3 to 5 clo at minus 25⁰ Celsius depending on air flow, which translates here to wind chill.

A cold store worker who is not dressed correctly will not achieve homeostasis, a core temperature of approximately 37⁰ Celsius, and will begin to feel cold.  The process of getting cold will make him uncomfortable and his body will automatically try and generate additional heat to return his core temperature to 37⁰.  To do this it will start shivering and then restrict blood flow to the arms and legs, also known as vascoconstriction.  If a worker’s core temperature falls to around 36⁰ he can no longer count accurately which is important to know if you are doing a stock count in a freezer store.

The common practice of providing warm up rooms for cold store workers where they are supposed to spend 10 minutes every hour is actually self-defeating.  Blood starts flowing to the arms and legs and returns relatively colder to the core.  After the 10 minute warm up, the worker’s core temperature will probably be lower than it was when he started his warm up.  Every time he “warms up” he is actually reducing his core temperature even further.  For productivity in freezer stores it makes sense to provide the correct tested clothing which will allow the worker to achieve and maintain homeostasis.

Keep your staff comfortable when working at sub-zero temperatures by clothing them in the best prossible protective wear.  Delf Coldwear is supplied to South African Coldstores by Barpro Storage.

James Cunningham