In Industries it is necessary to wear a protective mask, to protect the workers from the materials that are working with. In a woollen mill tiny hairs break off from the wool fibres and these will cause irritation within the lung if they are breathed in. During normal production the fibres are kept moist and they fall to the ground or machine ledges and do not cause any harm. If however these fibres dry out and become dislodged during cleaning they can be very dangerous, this is why it is necessary to wear a mask.
Most masks in use are of a simple paper filter type where air is drawn in through the filter and the fibres are caught on the outside, these are cheap disposable and easy to use but it is difficult to obtain an air tight seal between the mask and the wearers skin. Therefore other types of masks are used with very fine dusts, these have clear plastic visor.
Air is pumped in from a filtered source either a backpack or an external pump, which may feed several users, these masks are more expensive and restrictive to the user but they offer the highest level of protection against fine airborne dust.
Cleaning is often done with compressed air and this may move spots of grease into the air, which would be very harmful if they were to land in someone's eye. To stop this happening goggles are used to protect their eyes, the plastic is always clear and if the users require spectacles special lenses can be fitted. Welders wear special masks where the glass appears black and you cannot see out of it normally. When welders are working the electric arc that they are using creates such a powerful light that it would burn...