BOSTON (CBS) – It could be the most effective tool against rats since the Pied Piper Of Hamelin. The city of Boston is now using dry ice to reduce the rodent population.

It’s cheaper, safer and more humane according to Boston’s Commissioner of Inspectional Services, William “Buddy” Christopher.

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City workers, wearing protective gloves, dump handfuls of the dry ice directly into rat holes and burrows.

Dry ice is the solid form of carbon dioxide, and when it melts it turns into carbon dioxide gas. That trapped gas makes the rats suffocate.

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Four hundred pounds of dry ice costs only $225.

The city is experimenting with this tool and they say they’ve already had great success. One worker told us 24 out of 30 rat holes showed dead carcasses after one application.

Christopher told us dry ice is much safer for kids and other animals than poison. The city still uses poison as part of their arsenal.

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WBZ NewsRadio 1030’s Karen Twomey reports