Under heat stress conditions dehydration can seriously affect an employee's ability to function safely.
Dehydration effects can be minimised by encouraging employees to frequently drink cool water (rather than tea, coffee or carbonated drinks) in small volumes to compensate for water and metabolite losses due to sweating. Thirst is not a good indicator of dehydration – rather it should be considered an early indicator that you are starting to suffer from the effects of dehydration.
When working hard or at a high rate in heat stress conditions employees should consume around 250 ml (half a pint) every 15 minutes. This approach may not be practical due to the nature of the task, eg wearing PPE that restricts the ability to drink or working in industries where hygiene requirements prevent the consumption of food or drink. In these circumstances an alternative approach is drinking 500 ml of water per hour before work commences and encouraging the drinking of 500 ml of water during their rest periods.
This may meet their water demands during the work period but if water loss is significantly greater, then water intake should increase proportionately. Also even if workers replenish the lost sweat with equal amounts of water, they may still be susceptible to dehydration due to salt losses caused by excessive sweating. If you have employees exposed to heat stress conditions you should encouraging them to be adequately hydrated before they come to work.