Carbon dioxide has been used successfully for fumigation of stored products pests for decades. A recent study was done testing CO2 for bed bugs, and my take on it is that this may not be a reliable material for these insects. The researchers found that to kill 100% of the eggs of bed bugs required a concentration of nearly 100% carbon dioxide gas held for 24 hours. I just wonder how realistic it would be within an infested structure to hold that gas at that high of a level for that length of time. Using CO2 as the fumigant within a sealed chamber that holds household items would be a more realistic and reliable method though, as the interior gases could be held more effectively. 

Carbon dioxide is well known to be able to suffocate arthropods. Since bugs do rely on oxygen for their survival, removing that oxygen for certain lengths of time can kill them. The problem tends to be the eggs, which respire very little, and it takes longer to kill eggs of insects by oxygen deprivation than it does to kill adult or nymph stages that are more active and using oxygen more rapidly. 

Nitrogen gas would probably work in a similar manner. Our normal atmosphere contains about 78% nitrogen and 21% oxygen, so nitrogen is not a "toxic" gas. But, if we increase the level of the nitrogen it reaches a point at which too little oxygen is available and the animal dies by suffocation. For humans, increasing that nitrogen level just a few percent would be lethal. However, LIQUID nitrogen (which rapidly converts to the gaseous state) has been used in pest management, as has liquid carbon dioxide. As a liquid these are extremely cold materials. Liquid nitrogen has a temperature of MINUS 320 degrees Fahrenheit, making it a bit more dangerous to work with. A spill of that liquid on your hand would instantly freeze all tissues. 

Carbon dioxide, as a liquid under pressure in a cylinder, is more user friendly. The liquid is at a much higher temperature than nitrogen liquid and as it is ejected from a nozzle the CO2 converts to a freezing "snow" that is capable of instantly freezing any bugs that it is applied to. This is the basis of the Cryonite product for bed bug control. However, it is cautioned for both N and CO2 that high levels of these gases in an area are dangerous for the applicator, who needs to be certain the oxygen level in the air remains high enough to be safe. 

So, carbon dioxide may have a stronger future for our industry for chamber fumigation or as this freeezing snow applied to bed bugs and other pest insects. Conversely, we use steamers for bed bugs and roaches too, and even slight elevations of the temperature are sufficient to kill bed bugs and their eggs. Just 115 degrees held for 24 hours will kill all stages, so imagine how lethal it is to have 180 degree steam slam into the bed bug or its eggs. This is essentially instant death to the bugs.