Respirators

A respirator is a device that is worn over the mouth and nose to protect the wearer from occupational and environmental hazards such as harmful airborne particles and gasses. There are many different styles, and their functionality varies with the style. Not to be confused with a ventilator, which actually assists in breathing, respirators either forces air through a filter before it is inhaled or supplies an alternate, clean source of air for duration of time. It is common in the workplace in fields where workers are exposed to harmful chemicals, dust, debris, or gasses. There are two main categories: the air-purifying respirator, which forces contaminated air through a filtering element, and the air-supplied respirator, in which an alternate supply of fresh air is delivered. Within each category, different techniques are employed to reduce or eliminate noxious airborne contents.
For industrial uses, a respirator is often required under occupational safety guidelines. Workers who must work in areas where lead, asbestos, or other harmful toxins or hazardous chemicals are located are often required to wear one. Other uses include medical conditions, such as severe asthma or chronic obstructive pulmonary disorder (COPD) and personal protection from chemical or biological hazards.

When Respirators are Required?

Workers should use respirators for protection from contaminants in the air only if other hazard control methods are not practical or possible under the circumstances. Respirators should not be the first choice for respiratory protection in workplaces. They should only be used:-

• When following the “hierarchy of control” is not possible (elimination, substitution, engineering or administrative controls).
• While engineering controls are being installed or repaired.
• When emergencies or other temporary situations arise (e.g., maintenance operations).

Types of Respirators

Two basic types of respirators are:-

• Air-purifying; and
• Supplied-air respirators

Air Purifying Respirators

Air-Purifying Respirators (APR) are divided into two types: Particulate Filtering, which removes particulates such as dusts, mists, aerosols, and fumes; and Vapor and Gas Filtering, which removes vapors and gases from the air you inhale.
Air-purifying respirators (APR) are used under the following circumstances:-

• The wearer is determined to be physically qualified by a doctor.
• Contaminant identity and concentration are known; Concentration of oxygen is at least 19.5%.
• Work area is monitored.
• Respirator is approved for protection against the specific.
• Contaminant and concentration level.
• Successful fit-test is accomplished.

There are four common classes of APR face pieces:-

Disposable respirators (dust masks)

Provide protection against nuisance dusts and particulates.

Quarter mask respirators

Quarter mask respirators are used with cartridges or cloth filters. The quarter mask fits from the top of the nose to the top of the chin. The breathing resistance is high in comparison to larger masks.

Half-mask respirators

Half-mask respirators fit from under the chin to above the nose. One or two cartridges are used to filter the air and are discarded once the use limits are reached. The half-mask has approved cartridges for pesticides, organic vapors, dusts, mists, fumes, acid gases, ammonia, and combinations of these.

Full-face respirators

Full-face respirators protect the entire face. Full-face masks use twin cartridges, chin-mounted canisters, or chest- or back-mounted canisters. All cartridges approved for the half-mask are available for the full-mask. Several other cartridges are also available for the full-mask.

Particle-Filtering respirators

Particle-Filtering Respirators (PFR) provides a physical barrier to dusts, mists, fumes and fibers. The simplest PFRs are disposable and fit loosely over the nose and mouth. Filter pores become clogged easily and cause breathing difficulties. This makes frequent changing of the filter necessary. Disposable respirators protect against small amounts of nontoxic contaminants. More extreme hazards, like asbestos fibers, require a respirator with a replaceable filter that fits tightly over the face. A PFR does not protect against gases/vapors or oxygen deficiency.

Vapor and Gas Filters

Gases and vapors (from liquids such as solvents) are dissolved in the air and cannot be trapped with a particle filter. Gas and vapor respirators filter incoming air through one or more chemical containing cartridges or canisters. These chemicals absorb or chemically change the contaminant. They may also have a particle barrier. Some respirators contain more than one type of cartridge to filter several hazardous vapors at once. Cartridges are color-coded to identify which contaminants they filter. Refer to the National Institute of Occupational Safety and Health (NIOSH) for a list of color codes and the contaminants against which they protect.

Supplied-Air respirators

Supplied-air respirators provide a clean source of Grade D breathable air. They are used when work environments contain contaminants that APRs cannot filter out or in oxygen deficient environments. Supplied-air respirators are also divided into two types:

• Self-Contained Breathing Apparatus (SCBA):- where the air tank is carried by the user.
• Air Line Respirator where the air supply is some distance from the user and is supplied to the face piece by an air-line hose.

Supplied-air respirators are used in the following situations:

• Highly contaminated air often found in enclosed areas.
• Toxic gases are present.
• Oxygen deficient atmospheres where oxygen is deliberately.
• Replaced by another gas or chemically used up. (by fire or the rusting process).
• Air temperature is too hot or cold.
• Highly toxic environments like hazardous waste sites.

Supplied-air respirators’ disadvantages include restricted mobility and the possibility of kinked or damaged air-line hoses. The self-contained breathing apparatus (SCBA) is the respirator used for extremely hazardous environments. The SCBA consists of an air tank connected by a hose to a regulator that delivers 30 to 60 minutes of air to the mask. The tank is usually carried on the back.

A SCBA operates in one of two modes–demand or pressure-demand. In the demand mode when air is inhaled, negative pressure is created inside the face piece and breathing tubes. The negative pressure depresses the regulator’s diaphragm, opens the admission valve and allows air to be inhaled. Air flows to the face piece as long as the negative pressure remains.

A pressure-demand or positive-pressure mode SCBA maintains a positive pressure inside the face piece at all times. The system is designed to keep the admission valve open until enough pressure is built up to close it. Pressure builds up because air does not leave the system until exhalation. Internal face piece pressure is always greater than external air pressure. Any leakage from the face piece outward increases the protection.

Maintenance of Respirators

Respirators must be inspected before and after every use. Consider the following:-

• All parts should be clean and working properly.
• Check the face piece for dry rot, cracks, and holes.
• Perform a leak check.
• Replace valves and hoses if cracked, brittle or punctured.
• Check head harness for damage or deterioration.
• Tighten loose clamps or connectors.
• Check for proper filter selection and placement.
• Replace damaged or clogged filters

Following each use, respirators should be cleaned, disinfected and stored according to the manufacturer’s instructions. If respirator use is mandatory due to hazardous levels of airborne contaminants in the workplace, a Full Respiratory Protection Program must be developed and implemented. If employees are allowed to use respirators for nuisance levels of airborne contaminants, a Voluntary Use Respiratory Protection Program must be developed and implemented.