- Feed them less hay
- Feed them vegetables instead of hay
- Wet the hay
- Chop the hay into smaller pieces
- Buy a gigantic plastic enclosure like for hamsters from Amazon
- Enclose the cage with a roof
- Run a humidifier next to the cage
- Open the window in the middle of winter
It's the thought that counts, (they like the piggies and want them around) but I think I'll stick to vacuuming more and buying an air purifier.