Boric acid is a powder form of the result of a chemical reaction between boron and water. Boron on its own is a natural element in great abundance, mined from the earth. It is an odorless powder with no volatile substances. Place the finely ground powder in a squeezable container with enough air space left over to shake the contents. A small opening is effective in dispersing the powder over a small area.
Shake the container, loosing the boric acid powder, and then remove the cover. Squeeze the container so that a puff of powder escapes while you point in a specific direction. Allow the powder to settle. The coating should be so thin it is almost impossible to see. Heavier coatings discourage roaches from visiting the area.
Although boric acid has little toxic effect on humans, it is deadly to cockroaches, some spiders and fungi. As they walk over the boric acid powder, their legs pick up the granules. Later, when they preen themselves and ingest the powder, it kills them by desiccation.
Although boric acid does not harm humans, even children, do not to leave residues where children may play or contact the surfaces. Wipe down any surfaces where the powder settles after shaking.