Why Must The Clo Value Of Safety Footwear Be Included In Perceived Temperature Assessments For Road Workers?

Including the thermal insulation (Clo value) of safety footwear is essential because these items act as a significant thermal barrier, hindering heat exchange between the worker's feet and the environment. By factoring in the Clo value, safety models can move beyond simple air temperature readings to accurately reflect the total heat load on the body, ensuring that the risk of heatstroke is not underestimated.

Safety footwear does more than protect against physical impact; its materials and structure actively trap heat. To prevent heatstroke in high-temperature environments, thermal models must factor in the footwear's Clo value to reflect the true physiological strain caused by hot asphalt and limited breathability.

The Unique Thermal Environment of Roadwork

The Discrepancy Between Air and Ground

Standard weather reports only tell half the story for road workers. In high-temperature environments, asphalt surface temperatures frequently rise significantly higher than the atmospheric temperature.

The Foot as a Heat Entry Point

Because workers are standing directly on this super-heated surface, their feet become a primary contact point for thermal energy. The ground acts as a massive radiator, directing heat upward into the body through the soles of the feet.

The Dual Role of Safety Footwear

Protection vs. Breathability

Safety footwear is a critical component of Personal Protective Equipment (PPE). It is engineered with robust materials and rigid structures designed to defend against physical hazards like crushing or punctures.

The Insulation Factor

However, these protective features come with a physiological cost: thermal insulation. The structure that stops a falling object also creates a barrier that hinders heat exchange. This traps heat generated by the foot and blocks the dissipation of heat absorbed from the hot asphalt.

Why the Clo Value is Critical for Modeling

Quantifying the Barrier

The Clo value is the metric used to quantify the insulating ability of clothing and footwear. It provides a specific number representing how much a shoe resists heat loss and limits breathability.

Calculating Total Body Heat Load

To predict heatstroke risk accurately, you cannot view the worker as simply "standing in hot air." You must account for the specific equipment they wear.

Incorporating the Clo value allows thermal models to calculate the total body heat load. This ensures the assessment reflects the reality of insufficient breathability and excessive heat retention inside the boot.

The Risks of Incomplete Data

The Danger of Underestimation

If an assessment ignores the Clo value of footwear, it inherently assumes the feet are cooling efficiently. In reality, the feet may be overheating significantly.

False Security

This omission creates a false sense of security. A safety manager might deem an environment "safe" based on air temperature, while the worker is experiencing dangerous levels of thermal stress due to heat accumulation at the ground level.

Implementing Accurate Safety Assessments

To protect road workers effectively, you must treat footwear as a variable in your thermal equation, not just a static piece of uniform.

If your primary focus is accurate risk modeling: Ensure your thermal assessment software or calculations include the specific Clo value of the footwear currently in use, rather than generic clothing estimates.
If your primary focus is heatstroke prevention: Monitor the difference between asphalt temperature and air temperature; as the gap widens, the importance of low-insulation (low Clo) footwear increases.

True safety relies on data that reflects the worker's complete reality, from the heat of the sun down to the insulation of their boots.

Summary Table:

Factor	Impact on Road Workers	Why it Matters
Asphalt Temperature	Often 20-30°C higher than air	Direct heat source for the feet
Clo Value	Measures thermal insulation	Quantifies heat trapping in safety boots
Breathability	Reduced by PPE materials	Increases physiological heat stress
Heatstroke Risk	Underestimated without Clo data	Essential for accurate safety assessments

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References

Hankyung Lee, Chaeyeon Yi. Estimation of Perceived Temperature of Road Workers Using Radiation and Meteorological Observation Data. DOI: 10.3390/rs15041065

This article is also based on technical information from 3515 Knowledge Base .