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We are constantly reminded in summer that heat stress is an issue. Drink more fluids, keep out of the sun where possible and take a break when needed. But is the message really getting through? Are current warnings reliable for workers or is it a case of “crying wolf”?

Is Heat Stress Costing you?

WorkCover NSW states that, “In the three years to July 2011 there were 497 claims for workplace fatigue and heat stroke at a cost of $4.3 million to the NSW Workers Compensation Scheme”. This situation is likely to get worse. Maloney et al (2011) projects that the number of “dangerous”* days in Perth for an unacclimatised person doing physical labour will increase from 17 to 67 days per year by 2070.

Don’t cry wolf

Unfortunately, media reports commonly focus on inadequate indicators of heat stress like the forecast daily maximum temperature. Temperature, however, is not the only factor to consider when high heat stress events are imminent. High humidity, light winds and radiation all play equally important roles as well as level of activity, acclimatisation, clothing and fitness. Focusing on maximum daily temperature alone is likely to confuse people and can lead to poorly targeted actions for heat stress management.

The Thermal Work Limit – an all Australian heat stress indicator

The mining industry has made huge inroads in the understanding of conditions likely to cause heat stress through the development of the Thermal Work Limit (TWL) (Brake & Bates, 2002). TWL is the limiting sustainable metabolic rate that well hydrated, acclimatised individuals can maintain in a specific thermal environment, within a safe deep body core temperature (<38.20 deg C) and sweat rate (<1.2 kg/hr). It takes into account environmental conditions such as the wet and dry bulb temperatures, wind speed, globe temperature and pressure and individual conditions such as clothing moisture and thermal permeability.

KITE – Your own TWL forecast

Trying to piece all of these various data points together yourself can result in a high degree of error. As a solution to this problem Katestone have developed a targeted heat stress forecasting tool: KITE. kite-logo-smallKITE takes the guess work out of predicting potentially high risk conditions and uses the TWL at an hourly resolution out to seven days. This allows you to plan ahead for high risk conditions, and ensure appropriate precautions are taken.

Remarkably, if workers understand the signs of heat stress, are appropriately hydrated, and can self pace work, high heat stress incidents occur far more infrequently, accidents are reduced and everyone is happy.

‘Since the introduction of TWL-based policies in the Australian mining industry, the amount of man-hours lost due to serious heat illness has fallen from 12 million to 6 million, and the amount lost due to all heat illness incidences has fallen from 31 million to 18 million.’ Brake and Bates (2000)

*dangerous day = days when body temperature would increase by more than 2.5°C in 2 h)

Get in touch with Christine directly for more information on the benefits of KITE for your operations.

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