Like clean air, many of these hazards are invisible and odorless. Knowing the characteristics of each hazard helps to understand why respiratory protection is so important. Dusts, Fumes, and Mists - are tiny particles that float in the air. Dusts are formed when solid materials are broken down in activities such as sanding, grinding, or crushing. Fumes occur when metal is melted, vaporized, then quickly cooled, creating very fine particles that drift in the air welding and furnace work are likely to produce fumes.
Mists are tiny liquid droplets usually created by spraying, mixing, or cleaning activities.
Mists may be a combination of several hazardous ingredients. When hazardous dusts, fumes, or mists are breathed in, they become trapped in the respiratory system causing irritation. Short or long-term health problems may result, even death. Gases and Vapors - are invisible contaminants mixed in the air. Gases are substances that become airborne at room temperature.