I think a lot of people doesn't know how to filter an specific element from a mixture. So what you do is.
Select store and put where you want that filter. Use the property tool to set its ctype to the element you want to extract. Now the STOR will only absorb the particle you want to extract and you can then pass it to pipe or whatever you want.
an element that will only permit another element of its own ctype would be a good idea.
as far as I know, the best tpt can do right now to filter stuff would be one pixel at a time, and that would only work with powders, solids, and maybe gases? powders just fall, solids can be moved by pistons, but gases are way trickier because of diffusion.