Boilers at St Luke's Hospital which are causing the former hospital chimney to occasionally belch thick smoke, are to be replaced, Health Minister Joseph Cassar said in Parliament.

Replying to a parliamentary question by Leo Brincat, the minister explained that the smoke is caused by combustion when a switch is made between one boiler and another. When oil-firing equipment is switched on, accumulated oil is burnt at one go, causing a discharge of dark smoke. The emissions stop once the boiler flame stabilises.

Dr Cassar said the boilers are only being used to heat the water of the physiotherapy pool and to provide warm water for the patients at the rehabilitation wards.

The boilers are very old, the minister said, and the Foundation for Medical Sciences is expected to replace them with equipment using renewable energy.

The use of the chimney will be eliminated by the end of the year.