Personnel working in many hazardous industrial environments will need to wear breathing air masks or suits for protection, relying for their security on connection to the breathing air circuit. Craig Forrester, Stäubli Connectors UK manager, reviews some of the life-threatening hazards that can arise during use and how these can be eliminated.

The main factors to consider when using a breathing air circuit are that breathing air lines have to perform perfectly with total reliability. Any possibility of accidental disconnection or connection to the wrong circuit must be avoided. However, dangerous incidents resulting from accidental disconnection or connecting to unsuitable gases do still occur. The cause of most accidents could, however, be avoided by using connectors that are specifically designed for the job and are not an adaptation of standard compressed air connectors.

Breathing air connectors should be readily identifiable and require at least two distinct and separate actions to enable disconnection and they should be incapable of connection to any other circuits.

Many factory environments contain circuits for compressed air, gases and fluids and these are frequently positioned alongside a dedicated breathing air circuit. In many cases, breathing air lines are used infrequently and so are often located in less prominent locations. Accidental connection of the breathing air circuit to unfiltered compressed air, or other gases, is therefore a real danger. Identification is commonly assisted through the use of a distinct colour code for the breathing air circuit. However, a better solution is a unique plug profile that will mechanically only allow connection to the correct circuit, therefore eliminating any possibility of making a wrong connection.

A dedicated breathing air circuit can be made immediately recognisable through the use of distinctive colour-coding of the circuit, making it clearly stand out from the other circuits and connectors in the area. Stäubli, for example, has standardised on blue for all of its breathing air connectors and associated breathing air equipment.

Identification in the stores is equally important to ensure the correct item is selected for use on the breathing air circuits.

A safe breathing air connector should require at least two deliberate and separate actions to disconnect. Stäubli’s solution here is a connector plug which has to be pushed into the socket and then, by pressing on the release button, the coupling will safely disconnect. This conforms precisely to the safety requirements of the latest BS EN 139 Standard. Additional security against disconnection can be provided by padlocking the connector, a useful precaution where personnel using breathing air may be out of sight of the source.

Unsuitable air lines
Standard compressed air lines are unsuitable directly for breathing air usage. The air first needs to be filtered and pre-dried to at least instrument air quality. Instrument air can be used for breathing with the use of a second filter. Two-stage additional filtration is recommended, with the first stage being a sub-micronic filter eliminating any solid particles or aerosols and the second stage being an activated carbon filter for absorption of any oil vapour, aerosols and odour.

Typically up to four breathing air lines or masks can be connected to a portable filter unit with an inbuilt manifold, such as Stäubli’s BQR, which in turn, is connected to an instrument air supply.

The requirement for additional breathing air lines can be accommodated. In the event that a number of suits or masks need to be supplied directly from a dedicated breathing air circuit, a portable manifold unit eliminates the need to run separate lines back to the source. Stäubli’s manifold is capable of connecting six masks or half suits or four ventilated suits and is fitted with safety connectors with a unique plug profile to ensure that connection can only be made to the correct circuit.

For companies looking to install breathing air circuits it is important to determine the requirements at the initial design stage and never to compromise on the installation. Frequently, in the development of the workplace environment, the need for breathing air circuits is addressed late in the project, after many crucial decisions have already been made that could affect the breathing air installation. Further, it is important to always select products that have been specifically designed for breathing air applications and not those that have been adapted from standard compressed air designs.

Stäubli’s range of products has been designed for breathing air applications and has been fully tested in use. The plug profile is unique and not an adaptation of standard compressed air designs. The range includes all the elements needed to create and support breathing air circuits in industrial environments.