Thinkgood, I'm not sure exactly what you are asking but I'll take a stab at it.In general 314.29 2002 nec adresses acessability for j-boxes and conduit bodies.
In reguards to covers for j-boxes in an attic, yes attics are usually dusty but a standard cover is usually permissible. Also j-boxes and cables are to be protected from physical damage i.e.stepping on them. I prefer where possible to mount them to a vertical brace if possible to get them off the ceiling joists out of harms way.
