What is the Heat Stress at Work Warning? Amber, Red and Black explained
Under its Guidance Notes on Prevention of Heat Stroke at Work, the Labour Department operates a three-tier Heat Stress at Work Warning — Amber, Red and Black — to alert employers and employees to rising heat-stress levels for staff working outdoors or in environments without air conditioning. The system launched in May 2023 and was first revised in 2024; by late August 2026, the Labour Department tightened the trigger thresholds further and introduced a mechanism that automatically raises the warning by one level once the temperature reaches 35°C or above, responding to earlier criticism that Red and Black warnings had almost never been triggered even during record heat. In short, this warning system has been firing more often over the past couple of years, and employers and HR teams should stay current rather than treat it as old news.
It's worth noting that even after the August 2026 enhancement, public reporting confirms the Heat Stress at Work Warning and the Guidance Notes themselves remain administrative guidance, not standalone legislation — but that doesn't mean employers can treat it as someone else's problem. More on that below.
Does heat stroke count as a work injury? What the Employees' Compensation Ordinance says
Under the Employees' Compensation Ordinance (Cap. 282), where an employee meets with an accident arising out of and in the course of employment resulting in injury or death, the employer is generally liable to pay compensation — the core of the "no-fault" compensation system, which we cover in more depth in our EC insurance exclusions guide. A work injury isn't limited to obvious cases like falls or machinery accidents: where an employee suffers heat stroke, heat cramps, heat exhaustion or similar harm arising out of and in the course of employment because of a hot working environment, this is likewise treated as a work injury and falls within the Ordinance's coverage. See our complete Employees' Compensation Insurance guide for the full scope of coverage.
How does following the Heat Stress Warning relate to legal liability?
The Heat Stress at Work Warning isn't standalone legislation, but employers still carry a general statutory duty under the Occupational Safety and Health Ordinance to ensure the safety and health of their employees. These are two separate things:
- Compensation liability under the Employees' Compensation Ordinance — once an employee is injured by heat stroke, the no-fault statutory compensation liability is triggered regardless of whether the employer followed the guidance, meaning the employer is responsible for medical costs and statutory compensation;
- Common-law negligence exposure — if, while a warning is in effect, an employer takes no reasonable precautions at all (for example, arranging no hydration or rest breaks, or knowingly forcing an unwell employee to keep working), the employer may face further scrutiny over whether "reasonably practicable measures" were taken if held to account afterwards, which increases the size and risk of a civil claim.
A quick check: is your business higher-risk
Industries working mainly outdoors or in hot environments — construction and renovation contractors, couriers and food delivery, gardening, cleaning, security, and back-of-house kitchen staff — face particularly high exposure during hot weather. Even if your business doesn't fall into these categories, if any staff need to work outdoors or in spaces without air conditioning, this section is still worth your attention.
Without adequate EC insurance, a heat stroke injury is still yours to bear alone
Under section 40(1) of the Employees' Compensation Ordinance, employers must take out EC insurance to cover their liability under the Ordinance and at common law — this coverage doesn't distinguish between an accident being a fall or a case of heat stroke; as long as it's a work injury, it applies. Failing to maintain adequate EC insurance is a criminal offence carrying a maximum fine of HK$100,000 and 2 years' imprisonment; the bigger cost is that if a heat stroke injury does occur, the employer must bear the full statutory compensation and any common-law civil damages out of pocket — an amount that can far exceed the annual premium. If you're unsure whether your company's current EC policy's sum insured and scope are adequate for outdoor or high-heat-exposure roles, it's worth having a licensed advisor review it.
Source: Employees' Compensation Ordinance (Cap. 282); Occupational Safety and Health Ordinance (Cap. 509); Labour Department, Guidance Notes on Prevention of Heat Stroke at Work and Heat Stress at Work Warning (launched May 2023, revised in 2024 and August 2026).
3 things employers can do now
- Adjust work schedules to follow the warning — while a warning is in effect, shift outdoor work to cooler hours where possible, and increase the frequency of rest and hydration breaks;
- Put precautions in writing, not just verbally — a simple written record (rest schedules, hydration station locations) gives you something to point to if a dispute arises later;
- Review your EC insurance sum insured — especially if your company has outdoor or high-heat-exposure roles, check whether your existing policy's coverage actually matches that risk.