Health, Safety, Security and Environment

What Is a Self-Contained Breathing Apparatus?

4 min read

Sometimes a face mask just isn’t enough. Filtering low-quality air and preventing particulate matter from reaching the lungs is important. But what about when the air itself is toxic or if there simply isn’t enough of it to breathe in? For those situations, you’ll need something more.

Takeaway: Annual inspections are essential to making sure your SCBA will keep you safe.

What Is a Self-Contained Breathing Apparatus?

Self-Contained Breathing Apparatus (SCBA) is a respiratory protective device used to prevent users from inhaling:

  • Toxic gas
  • Contaminated particulate
  • Oxygen deficient air
  • Vapors
  • Other gases that are Immediately Dangerous to Life or Health (IDLH)

This device is used extensively in firefighting, nuclear facilities, chemical plants, steel works, and disaster prevention.

There are two major types of SCBAs used today: Open Circuit SCBAs and Closed Circuit SCBAs:

  • Open Circuit SCBA: Continually recycles or reprocesses air so that the user gets an uninterrupted supply of oxygen. Used in operations that tend to be very long.
  • Closed Circuit SCBA: Supplies air that is compressed to fit the cylinders, making them appropriate only for shorter periods of use.

Main Components of an SCBA

An SCBA typically has three main components:

  • A high-pressure cylinder or tank
  • A pressure regulator
  • An inhalation connection

All of these components are connected and mounted to a carrying frame.

Air Cylinder

SCBA Air cylinders contain about 1,240 liters (about 2,216 to 5,500 psi [15,280 to 37,920 kPa]) of compressed air at about 150 to 374 atmospheric pressure. This gives the user about 21 to 31 minutes of full rage air supply, depending on the working condition. When the air left in the cylinder is about 40 to 45 bars (serving the user for about 10 minutes), a warning alarm will be automatically sounded to alert the user to move out or get another cylinder.

The high-pressure tanks need to be constantly checked and refilled after use to make sure they are full the next time a worker needs to put them on.

Pressure Regulator and Reducers

As the name suggests, this component regulates the air from the air cylinder.

Air regulation works by using two valves. The demand valve supplies air to the mask, while the exhalation valve releases the air from the face mask.

Inhalation Connection/Protective Hood

This is comprised of a mask or mouth mask and mouth piece. It is designed to wholly covers wearer’s face and has a shatterproof visor that enables the user to see while allowing the required air to pass constantly.

The face mask should be softly molded in natural rubber and have a nylon neck strap and five adjustable head straps.

Factors to Consider When Selecting an SCBA

The SCBA’s intended use matters when it comes to choosing the product.

Type of Application

Industrial Use

The NIOSH industrial SCBA is suitable for confined space applications where the concentration level of IDLH gases is lower than that of contaminants, oxygen deficient environments, or where there is unknown contaminant concentration levels.

Given the many types of industrial applications, such as mining, nuclear, petrochemical, and chemical work, the SCBA design varies with its use.


Firefighters require an NFPA compliant unit. Since these standards are stricter, all SCBAs that meet them also comply with NIOSH requirements. Firefighting SCBAs are more expensive due to the exotic materials that are required to reduce the weight penalty and provide flame resistance.

Length of Use

The duration of tasks requiring an SCBA is an essential factor in selecting the right equipment. NIOSH confirms that supply tanks can be designed to provide 30, 45, 60, or 75 minutes of breathing air. However, the 30-minute SCBAs are generally preferred because of the comfort and cost.

Many people confuse NIOSH approved escape units with NIOSH approved SCBAs. Both have breathable air tanks, but the crucial difference is that the escape units can only be used for short periods of time. Since they are designed only for escaping oxygen deficient or toxic environments, they supply only 5 to 10 minutes of air.

Weight of the Equipment

The lighter the SCBA, the more comfortable it is to wear. Comfort is a key consideration for jobs that require wearing the equipment regularly. Weight is less important for SCBAs reserved for emergency use, such as unexpected maintenance in a confined space or closing a leaking valve.

Packing more air into a smaller cylinder is one way to reduce the weight of the cylinder. There are three pressure options:

  • High Pressure: used for 45, 60, and 75 minute SCBAs
  • Medium Pressure: used mostly in scuba diving
  • Low pressure: 30 minute SCBAs can be low or high pressure

SCBA Inspection

NFPA guidelines require annual SCBA functional testing. However, when the equipment is put through heavy and frequent use, testing should happen at shorter intervals to ensure the integrity of the equipment.

Most manufacturers follow the NFPA time frame and recommend an annual functional test and inspection by an authorized service center using authorized testing equipment.


Of all the equipment you use on the job, the SCBA is usually the one you can least afford to lose. In almost every case, it is your only source of safe, breathable air. That makes selecting the right one and properly maintaining it all the more important.

Check out the rest of our Personal Protective Equipment content here.

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