A frugal portable air cleaner

[Kaleva]

5. One could use a couple of gallon milk jugs filled with ice

If one has a chest or standup freezer, fill some clean gallon jugs part way with water (to allow for expansion) and put them in the freezer to turn to ice. After they froze, take one or more of the jugs and put them either behind or in front of the box fan but make sure they are placed in a shallow, leak proof container as water vapor in the air will condense on them. One can later use the condensate to water plants with. Keep one or more extra jugs of frozen water in the freezer to quickly replace the jugs that had thawed out so one doesn't have to wait for the jugs that contained melted ice to freeze again.

One could use quart milk jugs if one doesn't have the freezer space to handle gallon jugs.

It takes 144 Btus to change 1 lb. of water at 32 degrees into 1 lb. of water at 32 degrees. One gallon of water weighs approx. 8.35 pounds. One quart weighs approx. 2 pounds. It takes 1 Btu to raise the temperature of one pound of water one degree.

As one can see, it takes many more Btus to change the state of water then it does to change the temperature so having jugs of cold water in front or back of a box fan doesn't do much good except to act as a dehumidifier.