ABSTRACT
Respiratory protective devices are used for protecting the respiratory system from the inhalation of contaminants. Respirators should be used in an environment where the workplace is not safe even though improvements have been made, or where improvements are difficult or impossible. In principle, respirators are classified into two types: air-purifying respirators and supplied breathable gas respirators. Air-purifying respirators are further classified into non-powered and powered respirators. Non-powered respirators are generally small and are easily maintained. The powered air-purifying respirator uses a blower to pass contaminated air through filter element that removes the contaminants and supplies purified air to a respiratory inlet covering. Airline respirators are a type of supplied breathable gas respirator that use compressed air from a stationary source delivered through a hose under pressure. Respirators should be tested for their ability to face-seal and ensure protection for the wearer. The airflow resistance of particulate filters increases as the quantity of particles retained in the filter increases.
