Standardization in the Focus of the Wearer
Doesn’t the world have enough standards already? Do respiratory protective devices need to be standardized worldwide? What makes worldwide standardization of respiratory protective devices so difficult? How can we make a worldwide standardization of respiratory protective devices a success? Questions you might have heard about or even asked yourself.
A standardization group of the International Standardisation Organisation (ISO) – ISO TC94 SC15 – intends to create a new standard for respiratory protective devices (RPD). This international group of experts – coordinated by DIN – Deutsches Institut für Normung (German Institute for Standardization) – aims at implementing standardization with a new approach instead of the conventional proceeding. It is not existing devices or technologies that lead to requirements of a new standard, but the needs of the wearer are in the focus of the new standardization process. Via this approach respiratory protective devices worldwide will be designed, selected and operated according to application requirements.
The human being, the wearer is in the focus. His/her characteristics – in standardization language called human factors – determine the requirements of future RPD. It is not the device or design that is described but its features. Thus standardization ushers in a new era. For the first time human factors will be the basis on which to write a new standard.
The human factor – Ventilation rate
Human beings need breathable air or breathable gas to maintain their bodily functions. Depending on the strain human beings are exposed to they provide their organism with sufficient gas and oxygen contained therein, they breathe, supply the respective quantities of this gas – measured in litres per minute – to their lungs. This is also called ventilation rate or metabolic rate.
The more intensively human beings work the more oxygen is needed in their muscles. They breathe more intensively. The processes running during this are complex – it would go beyond the scope of this article to explain them in detail. But this correlation is important for the design and standardization of RPD. A respiratory protective device is to support the ventilation of human beings in all working environments described. For instance, in the future standard ventilation rates – breathing minute volumes – will be defined which allow for different classes of RPD. The highest class will be 135 L/min. since a human being – the wearer of RPD – is able to reach this breathing volume for a short time a few minutes long.
In case of operations where no extreme situations are to be expected, e.g. in case of control operations, an RPD with a breathing minute volume of the 50 L/min. class or less would be sufficient. The concept becomes clear: RPD are selected according to demand and must be offered and described in view of this.
A first document of this ISO series of the Human Factors, ISO 16976 Part 1-Metabolic rates and flow rates“ was published in autumn 2007 – the way is paved and more is to follow. Part 2 of this series deals with the anthropometry, the science of the body’s measurements.
An important criterion for safe support of breathing in contaminated atmospheres is the secure connection between the lung as the respiratory organ, especially mouth, nose and the RPD: This interface: mouth-nose is to be described. In this respect the facial shape is the decisive factor. And since human beings are rich in species and diverse, their facial features are also very diverse. The future ISO RPD standard is to include the 5th up to 95th percentile of all wearers grouped worldwide, i.e. a representative cross section of all facial shapes is to be captured. The American National Institute of Occupational Safety and Health – NIOSH – has started a project in which more than 3000 faces of adult working women and men of all races and of different age were measured three-dimensionally. A complementary study supported by NIOSH was carried out in China. The flood of data was analyzed and aggregated using a mathematical model, the ”principal component analysis“ (PCA).
Five characteristic facial and head shapes can be derived thereof: small, medium – this size covers 50 per cent of all wearers – short wide, long narrow und large. These shapes were produced from all available scan data in the respective segments using modern CAD systems. The data is used to produce test heads for respiratory protective mask testing and is also used to review the design of new facepiece geometries. In addition, the segmentation helps to assign test persons to different mask sizes when selecting suitable test persons for testing of the RPD suitability for practical use. ISO 16976-Part 2 standard summarises these results.
Breathable gas composition
Another factor – that of the breathable gas composition – determines the ability of a human being to act. For instance, oxygen and carbon dioxide must be available in the gas to be inhaled in concentrations that allow the RPD wearer to act without limitations. Limit values such as minimum oxygen concentration or maximum carbon dioxide concentration are described in another document, ISO 16976-Part 3.
Work of breathing
When breathing human beings carry out work. If they have to produce certain breathing pressures to overcome resistances like with using a RPD, this breathing work is perceptible. Also here, human beings are facing boundaries which can be put into values. The ISO standard writers also take up this issue and will provide another basic document with Part 4 of the ISO 16976 series “Work of Breathing and Breathing Resistance”.
Ergonomics implies various aspects since it summarises the regularities of human work. It deserves to be captured in more detail especially in view of the design and selection of RPD. This is what Part 5 of the series tries to depict. Here, aspects such as vision, noise, temperatures – both coldness and heat – as well as humidity are described in the limits that are tolerable by human beings, in order to ensure that the system man-machine, i.e. man-RPD works also in extreme cases.
If all these factors are available then and only then can a new standard for RPD be written which takes up these boundary values. The requirements of the features of a RPD can now be reasoned, derived and documented. An analytical process has started.
However, this process must not end with a safety-relevant description of the features of RPD derived from human tolerance limits being available. Also suitable RPD for the respective fields of application must be selected.
Is standardization to interfere here? The standardization committee SC 15 says: “Yes!” We must aim at making the procedures in this selection process comparable worldwide. This is the prime task of standardization. It goes without saying that overlaps with national, legal specifications cannot be avoided, but this must not destroy the approach towards a standard that supports the selection of RPD in the sense of a “guideline”.
The work with ISO 16975 “Selection Use and Maintenance” was started far ahead of the publication of the actual new performance standards, to ensure that at the same time the selection procedures and the notes concerning use and maintenance are available.
This document underlines the necessity of introducing a respiratory protective device range and refers to the risk assessment at the workplace. Without having performed a risk assessment no RPD can be selected and used in a target-oriented way – no matter how well described and designed it may be. A questionnaire systematically leads through this process. Each answer on a question leads the wearer to the next selection step. Also in the future we will distinguish between filtering RPD and supplied breathable gas RPD. Apart from the basic breathing-physiological and mechanical-physical features this classification also includes those features that can be derived from special applications usually known from fire brigades or mining operations. Hence, apart from basic requirements an RPD will have to cover requirements from these special fields of applications.
A specifically developed classification scheme takes up these dependencies and will at a later stage facilitate the comparability of different RPD types with respect to their features among each other. A RPD with the same classification will provide the same level of protection no matter whether it is a compressed-air breathing apparatus or a self-contained breathing apparatus – just to exemplify this.
Apart from these basic and special applications other parameters of the selection process are taken up. Characteristics of the individual wearers are asked for, as are the specifics to be expected during an operation: whether or not special tools need to be used, etc. and not least the ambient specifics. Listing of all requirement criteria results in a final RPD specification which is the basis for targeted procurement.
Hence, standardisation is a very complex process and requires a holistic approach. SC 15 is prepared to accept this challenge and is on a good way of implementing it. Started in 2002, with the elaboration of the human factors the SC 15 has formed the basis for successful standardization of RPD and can now turn to the part of describing the requirements of RPD features that was started in parallel. It is the aim to present a comprehensive set of new standards for RPD after another five years of intensive work, to ensure that the use of RPD protects wearers worldwide during their daily work routine.
Published: 10th May 2009 in Health and Safety Middle East