All dry food stuff is sealed in packaging and plastic containers.

There are other options, like adding a small vent fan to vent the crawl space to the outdoors, putting a dehumidifier in the crawl space, and having the crawl space "sealed" - basically spreading out big sheets of plastic on the ground and running them up the inside walls.

Often this isn't a paper throwaway filter like a central A/C has, but a section of wire or plastic mesh in the front grille that you can pull out and wash. 

They have industrial fans running in multiple rooms including the bedroom, kitchen and hallway and they are sectioned off with floor to ceiling plastic.

They may include painting the rooms for example but not to repair the plastic or to tape off the trim or scrape / clean walls.

The fan blade is relatively thin aluminum (older models) or plastic (newer), so don't go crazy when cleaning it.Tip: If you take the cover off, put the screws in your pocket, or put them in a plastic bag up on the kitchen counter. 

It's made from plastic milk/water bottles.

If so, parts of it have probably already been replaced with plastic (it rusts out). 

New electrical is better than real-old electrical with cloth insulation but not as good as 30-40 year old wiring with thicker copper wire and thicker plastic sheathing, so long as the sheathing isn't brittle. 

If you ever go to small claims court you will see landlords including in their cases charges like 79 cents for a broken toilet paper holder, or for $2 plastic drain stopper for a garbage disposer.