Experts on Friday urged employers to offer outdoor workers cooling products as summer approaches, saying they lower the risk of heat stress and heat stroke.

A study by the Occupational Safety and Health Council (OSHC) and Polytechnic University found that cooling vests were the most effective after testing the products on 30 workers aged 19 to 35, adding that portable fans and cooling collars were good alternatives.

Alex Cheung, a research assistant professor at the university, said workers won't tire as quickly if they use the products.

"We have observed that say, for example, if a participant without wearing any cooling device, then it takes around 15 minutes to complete the task," he said.

"If that particular subject, after putting on the cooling vest for example, it would allow the participant to say walk for 20 minutes. In that situation, there would be around 30 something percentage increment in terms of working efficiency."

He added that cooling devices could reduce the physiological burden on workers like reducing pulse rate and respiratory rate, and alleviate and delay work fatigue in hot environments.

Meanwhile, Bonnie Yau, executive director of the OSHC, said employers should also conduct heat stroke risk assessments for workers, after noting record-breaking monthly high temperatures this year.

"[They should] take preventive measures based on the assessment, such as providing shade, ventilation, drinking water, rest periods and reducing the work intensity," she said.

"It actually depends on the work environment, but say for construction workers where they are working strenuously and they have to work under the sunlight. Perhaps the cooling vest would be a very good product for them to consider."