The demolition industry defended its safety record in the wake of yesterday's Novena Ville accident in which a toppled excavator pinned and killed its operator.

Contractors insisted that such accidents are rare and that they have extensive processes and safeguards in place.

"Demolition is one of the highest-risk activities in construction," said project manager Richard Teo of CHL Construction.

"But if you look at statistics, (the number of injuries and fatalities is) not very high because people involved with demolition have to be careful."

Construction companies have to identify any potential problems that may arise from the demolition works.

"Before we do any operations, we do a risk assessment to evaluate all possible risks and precautions to take," said Straits Construction executive director Kenneth Loo.

He added that possible safety precautions include compacting the ground or using steel plates to spread the weight of demolition equipment, should it be unstable.

Construction firms are also required to submit a document called the "method statement" to the Building and Construction Authority (BCA) for approval, said Progressive Builders managing director Ng Yek Meng.

The document details the approach to and sequence of demolition, as well as any parts of the structure that would require specialised methods when tearing it down.

The statement differs for each project, said Mr Ng.

A plan for moving, holding and disposing of the resulting debris must also be drafted.

"All the steps for each demolition have to be carefully thought out and carried out according to the proposal by the professional engineer," he said.

Approval from the BCA usually takes one to two weeks, he added.

The Workplace Safety and Health Council issues technical advice for demolition as well as a compliance assistance checklist on its website, a spokesman told The Straits Times yesterday.

A code of practice for demolition came into force last November, added the spokesman.

Even after demolition work begins, an engineer is supposed to be on-site to supervise the work at all times, said Mr Ng. This engineer has the authority to stop the demolition if he is unsatisfied with safety conditions.

Mr Benjamin Tan, managing director of Ho Lee Construction, said: "The excavator usually won't topple that easily. You seldom hear of an excavator toppling and killing somebody.

"A crane has a boom, and if you are hoisting something and you're not careful, it might topple. But excavators have a very stable base and low centre of gravity."