Fire safety strategies for existing rock caverns in Hong Kong

• Rock caverns in HK are mainly used for public utilities with low occupant loads.
• Possibility of using caverns to house facilities of high occupant loads was explored.
• New fire safety strategies and upgrading of fire safety provisions are recommended.
• “Refuge area” protected by pressurization system should be introduced in caverns.
• Elevator/lift-assisted evacuation can be an alternative means to evacuate.

Rock cavern development is not a brand new concept in Hong Kong. In accordance with the recommendations of various studies conducted in Hong Kong, the use of rock caverns with high occupant loads is not impossible. All the existing cavern projects in Hong Kong, however, were designed to have low occupant loads and used as public utilities such as sewage treatment works, explosives depot, refuse transfer station, salt water service reservoirs and explosives magazine complex. In order to determine the possibility of utilizing caverns, from fire safety perspective, for potential uses other than public utilities with low occupant loads, this paper aims to critically review the fire safety strategies of the existing rock caverns in Hong Kong. The results of radon level measured in the largest rock cavern in Hong Kong are also demonstrated to determine whether cavern in Hong Kong is suitable for public use in terms of indoor radon concentration according to the relevant standard suggested by the World Health Organization. Further, recommendations are offered to facilitate possible utilization of rock caverns with high occupant loads in Hong Kong such as introducing new fire safety strategies and updating fire safety provisions for the existing rock caverns.