The demolition of the 14-storey Radio Network House will be "more challenging than average", says an implosions expert.

The central Christchurch building will be the first implosion in New Zealand, scheduled to take place at 8am on Sunday.

Queenstown 6-year-old Jayden Halliwell, who is undergoing cancer treatment while staying with mum Justine Swain at Christchurch's Ronald McDonald House, has been chosen to push the button.

Controlled Demolitions president Mark Loizeaux, whose company is in charge of the implosion, said the building was ''much more challenging than the average building''.

His company had been involved in about 9000 structural implosions, including more than 3000 buildings, with bridges, chimneys and the like also on the destruction list.

Loizeaux said the Christchurch building had been built much stronger than a building in a non-earthquake-prone area, such as the middle of the United States.

The Radio Network House implosion was not about the ''spectacle''.

''It's about risk management. If you can do something that reduced the risk to workers by 75 to 80 per cent, why would you not?''

He said other implosions in Christchurch could follow.

''Every single contract is keenly watching this,'' he said. ''They don't like putting their contractors on the top floors of these buildings.''

Loizeaux said he did not think implosions were exciting, but it was ''satisfying'' to see a job completed as planned.

The $1 million implosion would be carried out by a series of small explosives charges in holes drilled in the support columns of the building. A total of 60 kilograms of explosives would be used.

By carefully controlling the firing sequence, demolition would be achieved by using gravity, with the weight of the upper part of the building helping to destroy the lower portion.

Watch from home

Those keen to view the implosion are being asked to do so from home, say demolition contractors Naylor Love and Ceres New Zealand.

A video will be posted on press.co.nz shortly after, and television stations will livestream the action.

A public exclusion zone will be in place around the implosion site, with road closures in Madras, Gloucester and Worcester streets.

The demolition companies said dust was an "unpreventable byproduct'' of all types of demolition.

Dust from the implosion would be released over several seconds, but could linger in the area for up to six minutes.

Depending on wind speed and direction, the dust could potentially reach nearby properties, and the companies have advised the public to take the same precautions as they had been taking with dust generated by other demolitions in the city over the past 18 months.

The companies also advised those close to the implosion who found the dust to be uncomfortable or irritating, and anyone who had a respiratory condition that would be aggravated by dust, to stay indoors during the implosion.

All windows, doors and air intakes in the immediate vicinity should be closed and other openings that could allow dust to enter a building should be covered.

Any exhaust fans in use in the immediate area should be turned off for up to 30 minutes.

Seismographs between Radio Network House and nearby properties will measure the vibrations generated during the implosion.

The companies said a review of soil conditions in Christchurch and historic data indicated the vibrations generated would be below levels that could cause structural damage or even cosmetic damage.

However, people would be able to feel the vibrations, they said.

- © Fairfax NZ News

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