An industrial strength ozone generator
would almost certainly work, and would leave NO chemical residue. (I have chemical sensitivities, so I'm up on this stuff
) These units are used to turn hotel "smoking" rooms into "non-smoking" rooms. They are also used in fire and mold remediation.
These are not the same thing that you see in conjunction with air filters--these are much stronger and cost several hundred dollars to buy, but you can rent them for about $25/day if you shop around, and a day is all you need. They generate very concentrated ozone; you have to vacate the premises while it's in use, but once you air the ozone out, there is no residue at all, as ozone is just tri-molecular oxygen
gas. (Call a mold or fire remediation outfit from the yellow pages.) Or, if you're near Bend, Oregon you're welcome to borrow mine!