Dust masks
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Some people are more sensitive to the playa dust than others. In any case, having a dust mask on hand is usually a very good idea, even if you don't need it all the time. However, one advantage (even in a relatively dust-free tent) is that it will help retain the moisture in your breath, and keep your lips and sinuses from drying out. You have a ton of options for dust masks:
Cheapest
A strip of cloth, bandana, or sleeve cut from a t-shirt will filter out most dust and make breathing comfortable. It also tends to be more comfortable and look better than dust masks from a hardware store. However, if you need to sleep with a dust mask on, this isn't the way to go. These require frequent adjustment to keep the fit right, and will usually require a knot behind the neck.
A Few Dollars
Particle/dust/comfort masks from a hardware store. These come in many grades. The cheapest will cost you a couple of dollars for a 5 pack, but aren't comfortable to wear for long periods of time. The slightly nicer ones cost about the same, but come in 2-packs. These are a little thicker, softer, and more comfortable to wear. One nice thing about these sorts of dust masks is that you can draw on them with markers to make them a little more interesting.
One of the more highly recommended dust masks is the 3M 9211. It is both comfortable and does a good job filtering out playa dust.
Expensive
Someone who is really sensitive to the dust may want to consider a pollen mask. These tend to be designed for extended wear, and are very comfortable. They're also pretty expensive.
Another possibility is reusable neoprene dust masks. These are particularly suited for the playa in that they are comfortable, washable, and come in a multitude of colors.
Since these masks are made from form fitting neoprene, they are comfortable enough to wear while sleeping. This can be useful not only to avoid waking up with a mouthful of dust, but to also keep moisture in your body while you sleep.
One source for U2 neoprene dust masks is: The Allergy Store [1] .
