The general wisdom is that any sand (or loose substrate of any kind) is a risk for beardies. The main risk is of course, impaction, but sand can also cause irritation if it gets into beardie's eyes. Additionally, loose substrates tend to harbor more bacteria than solid, not as easy to keep clean unless of course, you plan to change it out often.
Some do opt to use play sand (the ONLY recommended sand for beardies), that is well sifted and cleaned. And this, ONLY for adult dragons, 1 1/2 - 2 years and up. No sand whatsoever is recommended for babies and/or juveniles.
Safest substrates for beardies are repti-carpet, slate, tile, shelf liner, or just plain old paper towel. If you look into the "viv pics only" thread in the "enclosures" forum, you'll find some great examples of what people have done, in particular, with slate and tile... some really nice vivs and ideas.
I went to the reptile shop, the best place i thought i could go for the right advice. They sold me a baby along with a bag of reptile sand. I had my Dragon on sand for four months and luckily he as been ok. Since i have been on here i have removed all the sand and bought some slate tile they look great and i'm looking for a nice peice of lino to cover the bottom. Some people feel sand is ok and i know people who use play sand.
Play sand is the only sand you can use and not with a baby beardie. One of my beardies has sand in his cage he had been kept on sand before I had him and he loves to dig but I used play sand that I screened. You just take some screen then pour the sand through it. That gets rid of all the bigger rocks and leaves the sand finer.
My other beardie has sand with tile on top of the sand. So then I do not have to cut the tiles right to exact size so it acts as a 2 inch grout line between the tiles. The sand is there to catch the liquids so I remove the dirty tile clean it and remove any sand that is soiled underneath.