A respirator is a specialized device designed to protect the wearer from inhaling hazardous atmospheres, such as dusts, fumes, gases, or vapors. This protective equipment works by creating a seal around the face to prevent airborne contaminants from entering the user’s breathing zone. Proper selection is necessary because different hazards require different mechanisms of protection, and an incorrect choice offers a false sense of security. Furthermore, a tight-fitting respirator must be correctly sized and tested for an adequate seal.
Air-Purifying Respirators
Air-Purifying Respirators (APRs) function by pulling ambient air through a filter, cartridge, or canister to remove contaminants. This mechanism requires the user’s lung power to draw the air through the filtering element, classifying them as negative-pressure respirators. APRs are only suitable for environments where the contaminant concentration is known and the atmosphere contains sufficient oxygen.
APRs are categorized by the type of contaminant they target: particulate filters and chemical cartridges. Particulate filters, such as the N95 or P100 series, physically trap solid or liquid aerosols like dusts and mists. Chemical cartridges or canisters contain sorbent materials, such as activated charcoal, which adsorb specific gases or vapors.
A major limitation of APRs is that they do not supply oxygen. They are prohibited from use in oxygen-deficient atmospheres (less than 19.5% oxygen) and environments classified as Immediately Dangerous to Life or Health (IDLH). The National Institute for Occupational Safety and Health (NIOSH) is the federal body responsible for testing and certifying the performance of these respirators.
Supplied-Air Respirators
Supplied-Air Respirators (SARs), also commonly referred to as airline respirators, deliver clean, breathable air from a source located outside the contaminated area. This external source is typically a high-pressure tank bank or a compressor, which must meet stringent purity standards for Grade D breathing air. The clean air travels to the wearer’s facepiece through a long hose, ensuring a continuous supply of safe air for extended work periods.
The primary trade-off for this extended duration of clean air is a significant restriction on the user’s movement. The wearer is tethered to the remote air source by the length of the hose, typically limiting travel to about 300 feet. SARs are often employed for tasks requiring long-duration protection in non-IDLH environments, or in combination with an auxiliary air tank for emergency escape from IDLH atmospheres.
Self-Contained Breathing Apparatus
The Self-Contained Breathing Apparatus (SCBA) provides the highest level of respiratory protection by supplying air from a tank carried directly on the user’s back. This design makes the wearer autonomous and independent of external air lines, granting unrestricted mobility. SCBAs are mandatory for entry into atmospheres classified as Immediately Dangerous to Life or Health (IDLH), including oxygen-deficient environments.
The compressed air cylinder, which is the “self-contained” component, typically holds a 30- to 60-minute supply of breathable air. This finite air supply necessitates meticulous time management and monitoring by the user to ensure a safe exit from the hazardous area. SCBAs are most often used by emergency responders, such as firefighters, for short-duration entry into extreme environments.
Choosing the Right Respirator for the Job
Selecting the appropriate respirator requires evaluating workplace hazards based on three primary factors: the contaminant nature, the atmosphere’s oxygen level, and the required duration and mobility. The contaminant type and concentration determine whether a filter for particulates or a cartridge for gases and vapors is necessary. If contaminant concentrations are unknown or exceed the maximum use limits of an APR, an atmosphere-supplying respirator (SAR or SCBA) is required.
The oxygen level dictates the fundamental class of respirator that can be used. If the atmosphere is oxygen-deficient (less than 19.5% oxygen), Air-Purifying Respirators are prohibited. Only a Supplied-Air Respirator or a Self-Contained Breathing Apparatus can provide protection, as they deliver air from an uncontaminated source.
Finally, the work duration and required mobility narrow the choice between the two atmosphere-supplying types. SARs are suitable for long-duration tasks in a fixed location where the user is not required to move far from the air supply connection. Conversely, SCBAs are the only choice for situations demanding high mobility and entry into IDLH atmospheres, despite the constraint of a limited air supply. All tight-fitting respirators require the user to undergo a medical evaluation and a fit test to ensure a reliable seal.