What you should know about SCBAs:

Self Contained Breathing Apparatus (SCBA) offer unique features for different applications. SCBAs are used in numerous industrial settings, from wall hanger application, meaning the user is required by rules and regulations to protect workers, but may never use the SCBA, to fire applications where the SCBA is used every day under extreme conditions.

SCBAs use compressed air cylinders, not oxygen, for breathing air. The cylinder duration can be from 30, 45 or 60 minute duration. This duration is based on 40 liters per minute which is slightly above normal breathing rate. Every SCBA manufacturer offers numerous accessories to fit the application of the user. Some of the accessories include supplied airline, allowing the SCBA air to come from an outside source, saving the cylinder for escape only. You will also have several choices on the style facemask. Depending on the type work that needs to be done, you will be able to use a tight-fitting hood for respiratory protection instead of a standard full face mask. The hood allows you to wear your own glasses and have long sideburns and still meet the OSHA standards for wearing an SCBA.

Over the last ten years, more electronic features have been added to the SCBA with added benefits to the user. SCBAs now have heads-up displays showing cylinder pressure on or near the facemask visor. All manufacturers also have data-logging capability that can be downloaded to a computer showing the time the SCBA has been used, cylinder pressure, temperature, and battery status. Some SCBAs have “Telemetry”, which allows data to be broadcast from an SCBA to a command area that can receive the status of the SCBA in a hazardous environment. Transmitted information can be cylinder pressure, real time temperature, and PASS status (Personal Alert Safety System). The command area can monitor the SCBA user and send a signal to the user to leave the hazard.

Communication has always been a concern while wearing an SCBA. There are numerous features that are now available to ensure clear communications. Microphones are now interfaced into the facemask, allowing the user to speak with clarity. Some companies offer throat and/or bone microphones that also provide clear communications.

SCBAs offer numerous features and the list is expanding yearly. Selection can be difficult. Check out the “Guide to SCBA Selection”

How SCBA’s Work:

Self Contained Breathing Apparatus have four main components: cylinder, a backframe that supports the cylinder, the pressure pneumatics, and the facemask.

Cylinder: The cylinder contains compressed air, grade “D” or better. The cylinder duration can be 30, 45 or 60 minutes with a pressure rating of 2216 or 4500 psi.

Backframe: The backframe supports the cylinder, pneumatics and any accessories that are attached to the backframe. Shoulder straps and waist straps allow the backframe to ride on the wearer’s hips, evenly distributing the weight of the cylinder and backframe.

Pressure Pneumatics: There is a two step process that allows the user to breath air from the cylinder. The cylinder valve connects to a pressure reducer which is usually close to the cylinder valve. When the valve is opened, air flows into the pressure reducer at 2216 or 4500 psi. The pressure reducer has a small chamber that the high pressure enters; using a piston and spring, the air flow is shut off when the pressure is approximately 125 psi. When the user inhales air, pressure is reduced in the chamber and more air enters while the reduced pressure air leaves the pressure reducer through a hose that is connected to the second stage regulator into the facemask.

As air enters the second stage regulator, often referred to as the mask mounted regulator, the pressure again gets reduced to a breathing rate that enters the facemask. As users inhale, air flows into the facemask. When inhalation is complete, pressure is slightly increased and the flow of air is stopped via a tilt valve or pilot jet block.

Facemask: The facemask has a clear visor and a speech diaphragm for communications. As air enters the facemask, air flows across the visor, reducing fogging on the surface. As the user stops inhaling, air stops flowing and as pressure builds up inside the facemask and the pressure build up allows the user to open the exhalation valve to exhale air. As the exhale pressure is reduced, the inhalation cycle starts again.

Other accessories are also attached to the pneumatics of the SCBA. Some SCBAs have a low pressure alarm, warning the user of low cylinder air depending on its use. This type of alarm is either a bell or whistle.

The designs of SCBAs vary among the industry. Some have complicated systems that can only be serviced by the manufacturer while others use a less complicated technology and offer training to users to do their own repairs. Check out the “Guide to SCBA Selection”.