Dry ice method..

[Neverend]

I've read about the dry ice method marty used to eliminate pests in his vivarium, and am interested to do it (though I don't have one). A great desire to eradicate the swarm of spider mites I have infesting my orchids makes me try out unusual (not to mention cool) methods. I'll be using a tank or pail as the CO2 'chamber'.

This is why I need to know, what is the minimum time I keep my orchid in the carbon dioxide 'chamber' in this case? The shorter the better, so I can treat all my plants quickly.