Hair - a person typically loses 50 hairs per day.

Lint - cloth material used in production for wiping purposes. Most wipes designed for use on      production lines are referred to as being "lint" free. This actually means free of loose surface      lint but as these are wiped across pad areas or stencils these cloths can snag and generate      lint. Using higher quality clean room cloths can eliminate this.

Fibers - fibers from clothing worn by operators can enter the production process.

Dust - much of the airborne dust is made up of human skin flakes. The average person breaths      700,000 skin flakes per day and sheds one layer of skin every 24-hours.

Plant sources - ceilings, floors, shelving and packaging materials are sources of particles.

Epoxy Dust - during PCB manufacture contamination removal systems are used at every step      in the process, however after routing only the top surface can be cleaned. The edges still      have loose dust attached. During packing and transport this dust is disturbed.

Glass Splinters - as PCBs are made from a fibrous material there is the risk of loose glass      splinters from routing or snap outs.

Solder paste - misprinted boards are often wiped "clean" and sent down the line again.

Solder resist - can flake away.

Packing materials - boards individually wrapped in paper can be affected by paper snaps which      attach themselves to the board by static.