The Medical Priority Despatch System (MPDS) - the controversial proposal to grade the urgency of each ambulance call, tabled recently in the legislature by the Fire Services Department - has been widely used for years in 22 countries, including the US, Canada and Britain.
Hong Kong will be the first in Asia to implement MPDS, a Fire Services Department (FSD) spokesman says.
It is expected to reduce calls for ambulance services and 'save lives', says FSD director Anthony Lam Chun-man.
MPDS categorises patients into different groups according to their conditions, and then despatches paramedics within a certain timeframe according to urgency.
Under the new system, there are five categories of urgency. For 'Category E', or immediate life-threatening cases, the ambulance team will arrive at the scene within eight minutes and 59 seconds, almost three minutes faster than the present pledge of 12 minutes.
However, for 'Category A', or non-serious cases, the arrival times may vary from 20 minutes to 50 minutes, depending on the patient's condition and resources available.
Mr Lam says the new system will save more lives, as those with immediate life-threatening cases can be reached faster. But both legislators and workers argue the move is putting people's lives at risk.
Many frontline workers say that people usually don't know how to report their condition on the phone, and operators may make mistakes in deciding whether cases are emergencies or not.
'A lot of people can't tell their condition - they don't know how to take a pulse or tell whether a person is conscious or not. It's dangerous,' one ambulance worker of seven years says, adding that even eight minutes is too slow to save lives in an emergency.
The consultation paper on prioritising ambulance services will be completed in September. Since it doesn't require a change in law, once the legislature approves the plan, the FSD can implement it quickly, after notifying the public.
Mr Lam refuses to say if the FSD will go ahead with the plan if there is strong public opposition.