More than 50 dairies around the country which police fear could be targeted by armed robbers are set to have "DNA" micromist spray installed that can be used to identify offenders as part of a $1.8 million police anti-robbery initiative.

The SelectaDNA spray, which contains a unique chemical that links offenders to crime scenes, is among three technologies that police are co-funding along with dairy owners whose shops have been identified as being vulnerable to armed robbery.

There has been a spate of aggravated robberies in dairies and petrol stations in recent months with offenders targeting cigarettes and cash. Charges have been laid against 1283 people around the country so far this year but figures specifically for dairies were unavailable.

The police will pay half of the cost of the micromist spray and two other security measures - fog cannons and sound barriers - with the shop's owner funding the other half.

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The spray, produced by SLS Security Group, is "non-confrontational" - it's activated by the shopkeeper when the offenders are in store.

As the robbers leave they are sprayed with a solution that's virtually invisible to the naked eye, but turns bright blue under UV light.

The solution stays on living tissue - like hair and skin - for up to two weeks and on clothing that's put through a washing machine for up to six months, SLS Security Group director David Morrissey said.

It also sticks permanently to items - such as a weapon - that may not be cleaned thoroughly.

"We need a size of a pinhead of that solution to irrefutably put the offender at the crime scene," Morrissey told the Weekend Herald.

"It works as a deterrent factor because there's no question that they were at the crime."

Although the technology is designed to prevent crime, it can and has been used in prosecutions of criminals in the past both here and overseas, providing evidence that a person was at the scene of a crime when it occurred.

A man who robbed a BNZ bank in Manukau in January 2014 confessed to the crime when told he had been sprayed with the micromist.

Superintendent Eric Tibbott, the police's national prevention centre manager, said the co-funding scheme was one of the first stages in a police initiative to prevent armed robberies at dairies.

"For me what concerns is the level of violence. It's gone beyond shoplifting. It's not someone going into a shop and stealing something and running out.

"These aggravated robberies ... it's the possession of weapons - knives, firearms, all sorts of offensive weapons are being used to threaten dairy owners and then it's the wanton violence of these individuals."

Staff from the police crime prevention team had identified nearly 200 dairies that met certain criteria which made them vulnerable to armed robberies and eligible for the co-funding initiative.

Stores that had been targeted in armed robberies before, as well as those in areas where crime was on the rise were among those at risk and were often eligible.

Auckland dairy owner Saiyad Shah tells the story of the night he almost lost his life during a robbery

Police had approached store owners to let them know about the scheme and 54 shops had opted in so far.

Each one would received the SelectaDNA spray, a fog cannon that released up to 700 cubic metres of fog within 60 seconds making it almost impossible to see anything and sound barrier devices that omitted four different frequency modulations at 125 decibels that confused offenders as the human brain could only deal with two frequency modulations at a time.

He hoped the three security measures would help prevent armed robberies, make dairy owners feel safer in their shops and help police catch offenders.

It was unclear how much of the $1.8 million had been spent at this stage, but police would have a better idea of how much money was left in the pool once more devices were installed and they had received invoices for the 54 installations.

"Our intention is to spread that money out as far as it will go," Tibbot said.

The three security measures had already been installed in two dairies.

An owner of one, who asked not to be named due to safety concerns, said he and his staff had felt safer since having the technology installed about two weeks ago.

Before the installation, his shop in south Auckland had been robbed three times in the past year or so.

During one of the incidents an offender pointed a gun at his head before a neighbour scared the man off.

His new security measure had given him a sense of comfort, knowing he wasn't defenceless.

Tibbot said dairies that weren't eligible for the co-funding initiative could still contact police if they wanted advice on how to prevent armed robberies.

"We want people to feel safe in the community and will do all we can for that to happen."