Gassing rodent burrows is not a new method. It has been used VERY successfully since the 1880s. As a matter of fact, before the Nazis made Zyklon-B infamous for their use in the death camps during WWII, the manufacturer of that product had been in business since the early 1900s selling it for commercial rodent control. Some US states that used gas chambers as their execution method during that time also used a sodium or potassium cyanide pellets dropped into a vat of sulfuric acid under the chair that the condemned inmate was strapped into. The chemical reaction produces hydrogen cyanide gas. At one point, exterminators in NYC also used this method to gas out rodent burrows but cyanides had been banned for use in pest control since the 1960s. They are JUST rediscovering this again, but with carbon monoxide gas...
On a side note, the IDF is now engaging Hamas fighters in the Gaza tunnels and they found out that the Islamists had brought a lot of women and children down there as human shields, so the IDF now have no choice but to fight it out mile by mile through the system. Previously, the IDF's plan for tackling the terrorist tunnels was to seal their entrances and exits with "foam bombs", which explode to fill enclosed spaces with tons of heavy and sticky epoxy foam that harden into cement-like consistency in an hour, eternally trapping Hamas fighters inside until they die of starvation, thirst, and suffocation. The presence of civilian hostages caused a complete scrapping of the original mission plan.
