Police will reintroduce handheld breath screening devices they pulled from service in October last year after doubts about the accuracy of the alcohol readings.

From tomorrow police will be redeploying 200 of its Draeger 7510 handheld breath screening devices in test mode following resolution of an earlier problem with some of the devices.

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In October 2015, Police withdrew 400 of the devices for testing as a precautionary measure, following discovery of a malfunction affecting the accuracy of alcohol readings recorded by 17 per cent of the machines.

Police also withdrew court action against 19 people prosecuted as a result of elevated breath test readings caused by the fault.

National manager of Road Policing, Superintendent Steve Greally says after a period of extensive scientific testing at its laboratory in Germany, Draeger had located and resolved the issue.

An independent review by a New Zealand expert had validated the steps taken to fix the problem.

'As a result of the issue being resolved, we will be initially reintroducing 200 of the devices in breath screening test mode only for the next few months to ensure they are working properly in field conditions.”

They'll then be brought back in for another round of accuracy tests, and subject to there being no further issues, all 400 devices will be reintroduced for use in evidential mode during August, Steve says.

'While we are confident in the steps taken to date to rectify the problem, it is critical that both Police and the public have full confidence in the accuracy of our breath testing devices.

'This is why we will be undertaking this further period of testing so we can be 100 per cent sure of their accuracy before putting them back into full service,” Steve says.

'This means that in the interim they will not be used for any evidential testing – which is required to prove a drink-driving offence or infringement – until Police is satisfied they are working properly.”

The Draeger 9510 devices will continue to be used for evidential testing.

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

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

'In response, Draeger has now changed its manufacturing process and construction of the devices, as well as the internal software to eliminate the problem.

'They have assured Police that the issues have been identified and resolved,” Steve says.

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