Heat Stress Rest

Why this matters

Cleaning, air-conditioner washing, outdoor work and indoor work without air-conditioning can all create high heat-stress risk in summer. Employers must carry out a heat-stress risk assessment and arrange rest breaks according to the Heat Stress at Work Warning (Amber/Red/Black) and the work rate. For the formal calculation, use the Labour Department / Occupational Safety and Health Council “Rest Time Calculator” and the latest Prevention of Heat Stroke at Work Guidelines (Third Edition, 2026). This guide is for occupational-safety reference only and is not legal advice.

Normal conditions (no warning)

- Light to moderate work: at least 10 minutes’ rest for every 2 hours of work

- Heavy to very heavy work: at least 15 minutes’ rest for every 2 hours of work

Workers who are not acclimatised or are re-acclimatising to heat, or who feel fatigued, require additional rest. Mopping, carrying water, washing toilets and washing air conditioners are usually moderate to heavy work.

Warning in force (outdoors / indoor areas without air-conditioning)

Amber = high; Red = very high; Black = extremely high. Arrange hourly rest breaks where necessary.

Basic outdoor open-air rest per hour:

- Amber: light—; moderate 15 minutes; heavy 30 minutes; very heavy 45 minutes

- Red: light 15 minutes; moderate 30 minutes; heavy 45 minutes; very heavy suspend work

- Black: light 30 minutes; moderate 45 minutes; heavy suspend work; very heavy suspend work

“Suspend work” means stop immediately. Shade, ventilation, fans, mechanical assistance and other controls may increase or reduce the rest requirement according to the risk assessment; even if the calculated requirement becomes 0, the normal minimum of 10/15 minutes for every 2 hours must still be followed.

On site

1. Check the warning before work starts; provide shade, water and a cool rest area

2. Drink water regularly

3. Rest in a cool, well-ventilated place

4. Rotate between hot and cool areas; avoid heavy work during the hottest periods

5. Give new staff and workers returning after a long leave more rest

6. Stop work, cool down and notify the supervisor for headache, dizziness, extreme thirst or nausea; seek medical attention if severe

References

https://www.labour.gov.hk/common/public/oh/Heat_Stress_GN_tc.pdf

https://noheatstress.hk/

https://www.labour.gov.hk/common/public/oh/Heat_Stress_GN_en.pdf