One downside to living on a farm is I track in a lot of dirt. Everything in my house collects dust; I mean everything including my houseplants. Aside from looking grungy, a dirty plant can't breathe because the pores in the leaves clog up. The solution is simple; give them a bath.
For small to medium plants you can just wash the leaves by wiping with a sponge or cloth soaked in lukewarm water. Add a little soap if the dust is really encrusted, but make sure you rinse it off. You can also wash houseplants at the sink. Hold your hands over the top of the pot to keep the soil in, and gently wash the foliage.
Or how about a shower? You can put large plants in the shower, but be easy with the water pressure. You don’t want to damage the leaves.
Now these techniques don't apply to all plants. Plants with fuzzy leaves like African violets resent having water on their foliage. Use a dry brush to remove the dust.
Now remember whenever you are using these techniques involving soap, be sure you get it all rinsed off.
The next time you're giving your plants a little TLC; don't forget to give them a bath.