Evaporative Cooling

Each year, millions of Muslims gather in Makkah for Hajj, one of the world’s largest religious gatherings. However, rising temperatures are making this spiritual journey harsher. In June 2025, temperatures exceeded 50 degrees C, similar to Hajj 2024, which recorded a high of 51.8 degrees C. That year, more than 1,300 pilgrims died from heat-related causes, most of them unregistered and without access to cooling or shelter (Associated Press, 2024). On June 16, 2024, over 2,764 cases of heat exhaustion were reported in a single day (Arab News, 2024).

In response, the Saudi government made significant improvements for Hajj 2025. These included more than 10,000 new shaded trees, over 2,400 misting fans and the operation of the Grand Mosque’s 155,000-ton cooling system to maintain temperatures between 22 degrees C and 24 degrees C (Saudi Press Agency, 2025). As a result, a 90% reduction in heat-related illnesses was reported compared to the previous year (Financial Times, 2025).

Even with centralised efforts, millions of pilgrims still required decentralised and mobile cooling solutions, especially in outdoor or semi-covered areas.

Cooling outdoor zones with fog cannons

For large, open areas exposed to direct sun, such as the paths to Jamarat, gathering zones in Arafat and Mina, high-pressure fog cannon systems played a vital role. The systems spray ultra-fine water droplets into the air, reaching up to 70 metres, quickly reducing ambient temperature by 10-12 degrees C (International Journal of Heat and Technology, 2021).

Compared to small misting fans, fog cannons cover wider areas with stronger airflow, making them more effective for crowd cooling. The units are mobile, lend themselves to rapid deployment, and can be operated successfully alongside hydration stations and heat-reflective white roads. Fog cannons offer practical, low-energy solutions that significantly reduce heat stress in zones where traditional cooling is not possible.

Using IDEC units in tunnels and shaded walkways

While fog cannons work well in open spaces, other areas, such as tunnels and covered walkways need a different solution. Indirect-Direct Evaporative Cooling (IDEC) systems are the best solution for shaded and semi-enclosed zones.

Hundred per cent fresh air, no hot exhaust

Unlike regular air conditioners that re-use indoor air and blow hot air outside, IDEC systems work differently. They take in fresh air from outside, cooling it down from 50 degrees C to anywhere between 13 degrees C and 18 degrees C, using water-based evaporation; they, then, send the cooled air into space. After use, the air is released outside. This not only improves indoor comfort but also helps cool down nearby outdoor areas, reducing the “heat bubbles” often created by traditional air conditioning systems in crowded spaces.

Energy efficiency and environmental impact

Traditional air conditioning units recycle indoor air and release hot exhaust into the environment. IDEC systems, in contrast, are sustainable. They use no refrigerants and consume up to 85% less energy than conventional air conditioners (Ahmad et al., 2024). With global demand rising, the IDEC market was valued at USD 1.2 billion in 2024 and is growing fast, especially in hot and dry regions, like large parts of Saudi Arabia. IDEC systems support sustainability goals as well as the striving for lower operating costs.

A sustainable model

Saudi Arabia’s Vision 2030 aims to promote sustainability, energy efficiency and reduced carbon emissions. IDEC systems support these goals by offering low-energy and environmentally friendly alternatives to traditional cooling systems. In the future, heat risks will continue due to climate change and unexpected temperature spikes. Makkah’s average temperature is increasing at a rate of 0.4 degrees C per decade (Pal & Eltahir, 2016). According to the study, the carbon footprint per pilgrim during Hajj is about 60.5 kilograms of CO₂ equivalent per day, much of it linked to cooling systems (Al-Ghamdi et al., 2011).

Integrating low-energy, low-emission technologies like IDEC and fog cannons will be essential to reducing environmental impact while maintaining comfort and safety.

Conclusion

Hajj 2025 demonstrated that innovative, scalable cooling solutions can make mass gatherings safer without compromising on sustainability. Evaporative solutions brought broad-area cooling in the open sun, while providing efficient, fresh-air cooling in shaded and enclosed locations.

Together, these solutions can form a powerful model for outdoor climate control. They not only can address immediate heat challenges but also align with broader environmental goals. As climate risks continue to grow, these systems are poised to become essential for Hajj, Umrah and other outdoor events.

The writer is Co-Founder, Windmason Arabia Company. He may be reached at shakeel@windmason.com.