You need a mix of soapy (detergent) water only for spider mites, preceded by a really good hard spray of water, followed by another soap session 5 or so days later, and another one after that, to get eggs, etc. which may not have been killed the 1st or 2nd time. Also, mites don't like humidity, so the higher the better... see how often you can hose down foliage front and back.

You can even skip the soap and just go with the jet spray of water. You do it every day or two and they will migrate somewhere else. They hate water.

randy

I liked the idea of CO2 to kill off spider mites. But I guess you did not get any good answers. High levels of CO2 are used to accelerate plant growth in studies at Purdue. You might try using it just during daylight hours as plants take up CO2 during the day and give off O2. At night plants however they do respiration using O2 so you would not want to kill the plant. I would guess that some 6 to 8 hours of CO2 would kill the mites. A good subject for a MS thesis. Try a google search.
Yes, the CO2 could be generated using sugar water and yeast with equipment used in wine making. Perhaps small cylinders of CO2 could be purchased but you must be sure that source of CO2 is purified.

Humidity will deter the little buggers I have used systemics that seems to be the most effective.

I have recently tried K+ Neem by Organica this seems to work fairly decent but it is expensive