Malfunctioning breath alcohol screening devices used by police are set to be replaced.

From tomorrow police will be replacing 200 of its Draeger 7510 handheld breath screening devices in test mode after discovering 17 per cent of the machines are faulty.

The malfunction caused elevated alcohol readings, and forced police to withdraw court action against 19 people prosecuted as a result of the inaccurate devices.

Police stopped using 400 of the devices as a precautionary measure in October last year.

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Testing identified that the problem was caused by a malfunction in the device's silicon bellows mechanism, which controls the amount of air that can be blown into the machine.

This meant that when calibrated, some of the devices did not accurately record breath alcohol levels, resulting in elevated breath alcohol readings for some people.

All of the costs associated with the withdrawal, testing and redeployment of the devices to date are being met by Draeger.