Dehydration Risk Assessment

Understanding and managing heat stress on the worksite can be a challenge due to the many factors which influence the risk of heat stress. Additionally, even at cold temperatures workers can be at risk of dehydration. The following tool, adapted from the 2013 AIOH Heat Stress Guide, allows you to better understand the factors that increase the risk of heat stress on your workplace.

Workplace Hazards
The following factors influence thermal risk. Select which option best describes your worksite.
Sun exposure
Indoors Full shade Part shade No shade
Work area surface
Neutral Warm on contact Hot on contact Burn on contact
Exposure period
< 30 min 30 min - 1 hour 1 hour - 2 hours > 2 hours
Confined space
Task complexity
Simple Moderate Complex
Stairs / Ladder
None 1 level 2 levels > 2 levels
Distance from cool rest area
< 10 m 10-50 m 50-100 m > 100 m
Distance from drinking water
< 10 m 10-30 m 30-50 m > 50 m
Clothing (permeable)
Single-layer (light) Single-layer (mod) Multiple-layer
Understanding of dehydration
Training given
No training
Air movement
Strong wind Moderate wind Light wind No wind
Respiratory protection
None Disposable half face Rubber half face Full face
Metabolic Work Rate
More physically taxing activities increase thermal risk. Select which option best describes your worksite.
Metabolic work rate (?)
Light Moderate Heavy
  • Light Work: Sitting or standing to control machines, hard and arm work assembly or sorting of light materials.
  • Moderate Work: Sustained hand and arm work such as hammering, handling of moderately heavy materials.
  • Heavy Work: Pick and shovel work, continuous axe work, carrying loads up stairs.
Apparent Temperature
Working at high apparent temperatures greatly increases thermal risk. Fill in the weather parameters to calculate apparent temperature, or enter the apparent temperature of your worksite directly.
Calculate apparent temperature
Temperature °C
Relative humidity %
Wind speed km/h
Or, enter apparent temperature directly
Your Risk Assessment
Fill in all fields to obtain your thermal risk assessment.
This thermal risk assessment tool is to be used as a guide only. Your requirements may differ due to employee health conditions and other site-specific factors such as impermeable PPE.
Thermal risk assessment tools are great for estimating thermal risk across your workplace. MX3 Hydration measurements allow you to personalise these risk assessments further by identifying workers which are atypically dehydrated or need extra attention.
Hydrated (≤ 65 mOsm) Mildly dehydrated (65 - 100 mOsm) Moderately dehydrated (100 - 150 mOsm) Severely dehydrated (> 150 mOsm)
Before work After work
Click on each hydration category to find out how this information could be applied on your worksite.
For increased accuracy with regard to personalized hydration assessment, MX3 recommends baselining of workers to establish their fully hydrated optimal hydration zone (OHZ).

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