Bring out your yellow fire extinguishers - the Environment Ministry wants to destroy them safely because of their threat to the ozone layer.
Many of the extinguishers are thought to be owned privately and are possibly unsafe, because they are likely to be corroded inside.
But they cannot be legally serviced orre-charged.
The extinguishers contain a firefighting gas, halon 1211 or bronchochlorofluoromethane (BCF), which reacts chemically with the ozone layer.
Halon 1211 is more destructive than other chlorofluorocarbons: one yellow 1.4kg extinguisher contains enough gas to destroy 27 tonnes of atmospheric ozone over 17 years.
There are thought to be up to 110,000kg of halon 1211 left in hand extinguishers in New Zealand.
Most of them are more than 12 years old, and they have been barred from servicing or refilling, says John Fraser, chief executive of Auckland non-profit company Halon Recycling.
He says many of the extinguishers are corroding inside.
This could cause pinhole leaks through which the nitrogen propellant gas or halon could escape.
A fire would not be put out unless at least 6 per cent of its air supply was saturated with halon.
Mr Fraser says the Government is helping to pay for the destruction of the gas in hand extinguishers.
It normally costs $20 a kilogram to ship the gas to Australia for incineration. The Government will pay $5 a kilogram towards that.
Many fire protection companies are offering discounts on dry powder or other replacement extinguishers, which will offset the recycling cost.
The cylinders were distinctive and popular in the late 1970s and had a reputation as one of the best extinguishers for electrical fires. Hundreds are thought to remain in workplaces, private cars, caravans and boats.
New Zealand is a signatory to the Montreal Protocol which commits countries to eliminate the use of ozone-depleting substances. The protocol requires them to be destroyed by this year.
Mr Fraser says safety considerations mean householders should replace the yellow extinguishers anyway, rather than risk fighting a fire with one which might not work because of age or leaks.
