Final answer:
Men used poison gas to scare the rats out of the burrows, which is effective against pest infestations in food storage areas.
Step-by-step explanation:
The men pumped poison gas into the burrows to scare the rats out. This method is mentioned as a way to deal with rat infestations in areas where food, like meat in storage rooms, is present. The poisoned gas would be dangerous to pests like rats without adding moisture that could exacerbate food spoilage, unlike water. Unlike smoke which is detectable and might also preserve the meat in an unintended way, gas is typically clear and more insidious, often designed to be lethal to the pests upon inhalation or contact.