EPD inspectors conducting visual inspection inside an enclosure, just after removal of asbestos plaster from the ceiling.

Asbestos Abatement in An Occupied Building

W.Y. FONG

    Dressed in protective clothing similar to a space-suit, Philip, a senior EPD inspector, was standing on top of a ladder and holding his torch close to the ceiling. "Hey, John, look at these fibres. You must clean here thoroughly again", he shouted to the asbestos contractor when he found shadows of fibres from the torch beam on the ceiling surface.

The success of an asbestos abatement project such as this one requires careful planning, sophisticated skills, and a very high standard of work. This is very important for safeguarding the environment, the health of workers involved and the health of nearby and future occupants.

Philip was conducting a visual inspection inside an enclosure where the removal of asbestos acoustic plaster from the ceiling had just finished. Since breathing in asbestos fibres could lead to fatal diseases, he had to put on protective clothing and a respirator before he went into the enclosure.

The enclosure was yet to be certified to be clear of contamination by asbestos. Philip had to make sure that it had been cleaned to a high standard, and was free from visible debris and fibres.

As usual, the room would be re-occupied afterwards. He had to be very careful to have every corner examined, and to verify that it was free from asbestos contamination.

As with all other cases, this project was carefully designed and planned. Successfully completed in June 1996, it was the biggest and the most complex asbestos removal project in an occupied building in the territory: to remove asbestos plaster from 200m²; ceiling on each of the floors and the two basements in a nine-storey social service centre in Tsim Sha Tsui. The difficulty was the need for the centre to maintain services to the public during the entire period of the asbestos removal work.

In this particular project, the Architectural Services Department, as the coordinator, had to answer the following questions before work could start:

  • whether to vacate the whole or part of the building for asbestos removal work. It was necessary to minimize the disruption of services to the public, and to avoid hazards posed to the occupants. Many children were using the building and they were more vulnerable to asbestos exposure than adults;
  • whether there was asbestos inside the pipe riser ducts and above the ceiling. These areas were not assessible for preparatory inspection, as otherwise the surface asbestos materials would be disturbed while occupants were still around; and
  • whether thorough decontamination of the central air duct running from roof to basement was necessary, as asbestos fibres might have been released from the asbestos plaster over the years and deposited inside the ductwork.
The Architectural Services Department ran a trial removal to find out the answers, by removing the asbestos from part of the 7th floor in October 1992. The trial also provided information on the time required for asbestos removal on one floor, the possible cost involved, and the reactions of the occupants with asbestos removal work next to their work place.

The main project eventually started in June 1995. Work started on the ground floor and lower ground floor first to provide an asbestos free access to the building later.

The EPD conducted visual inspections to the enclosures and took samples, to check that the specialist asbestos contractor was conducting the asbestos removal work properly.

In addition to 600 air samples collected and analyzed by the accredited laboratory engaged by the contractor to monitor the fibre levels outside the enclosures, the EPD's asbestos laboratory also conducted independent air tests to countercheck the air monitoring results.

After visual inspections confirming that the enclosures were free from visible fibres, the Architectural Services Department sought support from the Government Laboratory to conduct clearance air tests to measure the concentration of invisible fibres inside the enclosures. The contractor could remove the enclosures for re-occupation only after clearance air tests results were satisfactory.

To make sure that the air ducts were cleared of invisible asbestos fibres, the Government Laboratory conducted air tests to the air ducts by scanning electron microscopy, a very sophisticated method for accurate measurement of low fibre concentration. All test results were satisfactory.

The success of an asbestos abatement project such as this one requires careful planning, sophisticated skills, and a very high standard of work. This is very important for safeguarding the environment, the health of workers involved and the health of nearby and future occupants.

On 1 May 1996, the EPD started registration under the Air Pollution Control Ordinance of asbestos professionals and laboratories. The registration system enables only those people who possess the required academic knowledge, training and experience to be registered with the Government for conducting asbestos removal work. As a result, neighbours of asbestos abatement work sites can feel comfortable. They need not worry about whether the contractor engaged in the work has the knowledge to do the job properly or whether they are exposed to unreasonable risks arising from any asbestos removal work.


Special air movers equipped with high efficiency particulate air (HEPA) filters installed to maintain slight negative pressure in the enclosure, to prevent the release of asbestos fibres from the enclosure.

Collection of air samples by EPD at exit of an enclosure to check for release of asbestos fibres from the enclosure.

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