Hong Kong enhances heat stress warning system after chorus of criticism, but rules still not binding

Hong Kong's Labour Department has upgraded its heat stress warning system following criticism that the previous thresholds failed to activate alerts during a record-breaking heatwave this month. The revised Heat Stress at Work Warning (HSWW) system will have two additional trigger conditions starting Friday to better safeguard workers in high-temperature environments. Although these changes make the system more sensitive, the rules still do not legally bind employers.

Under the modifications, the monitoring threshold for activating higher-level warnings will be lowered when the Hong Kong Observatory (HKO) issues an "Extremely Hot Weather" Special Alert. When temperatures in Hong Kong reach 35 degrees Celsius or higher, the system will automatically raise the warning level by one step, moving from amber to red, or from red to black.

The system drew criticism earlier this month when the alert remained at amber despite Hong Kong experiencing its hottest day in 143 years on August 9. Former Hong Kong Observatory (HKO) director Lam Chiu-ying expressed bewilderment that the record-breaking temperatures only triggered the lowest-tier Heat Stress at Work Warning. Two additional former HKO chiefs joined him in calling for a system overhaul, highlighting that the Labour Department relies on the HKO's Heat Index (HI) as a reference for the HSWW, which is more suitable for the general public than outdoor workers.

They suggested the department adopt the wet-bulb globe temperature, a globally recognized measure of environmental heat that considers factors like humidity, radiation, and air movement in addition to air temperature. While the department has not yet adopted this recommendation, it stated it will consider it in the future.

The local charity supporting workplace accident victims welcomed the lowered thresholds, believing they would enhance the HSWW system's sensitivity in addressing heat stress experienced by workers. The Association for the Rights of Industrial Accident Victims urged the Labour Department to review the enhanced system annually and consider incorporating the wet-bulb globe temperature as a reference point.

The NGO also called for the government to mandate an immediate halt to high-risk outdoor work during a black heat stress warning, while allowing workers to take rest breaks during lower severity warnings without facing penalties from their employers.