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 …showed first 75 words of 461 total…

…showed last 75 words of 461 total…out such as drains, empty vats and large enclosed tanks. Gases such as methane, hydrogen sulphide, carbon monoxide and carbon dioxide may gather these are poisonous gases, which cannot be filtered out so the worker must be protected from them. As none of these gases can be allowed inside the mask fresh air is supplied from an out side source at high pressure. The mask is usually a full-face mask or a compressed air hood.