PIMEX (Picture Mix Exposure) allows the flow of work to be filmed with a video camera and simultaneously exposure data to be recorded by means of sensors and transducers attached to the workers. The exposure data are added to the video by means of special software. The activity of the worker is linked at any time to the recorded exposure values. Originally it only covered chemical hazards. Today it can process a large variety of physical and ergonomic factors. The system motivates to change the work process until satisfactory results are achieved. The tool facilitates discussions to achieve optimum solutions.
In the early 1980s Gunnar Rosén and Ing-Marie Andersson from the Swedish Arbetslivsinstitutet (National Institute for Working Life) in Stockholm were looking for a solution for a typical problem in measuring exposure data: A typical problem arising from later analysis of the data was that reasons for peaks in the measured values were difficult to explain, even if the exact time of occurrence was known . They were thinking of combining data from measurements of hazardous substances with video records. When they successfully developed their first prototype, they called the system PIMEX as an abbreviation for Picture Mix Exposure . Almost at the same time, in the USA, research on a similar system was being conducted . In the late 1980s continuously improving sensor, video and computer technology, along with falling prices, facilitated the development of an initial system that was able to gather exposure data, combine these with the work process videos, and display both video and data on a monitor .
In the following years, different institutes from several European countries took up the idea and developed the system further . Major steps were introduced for example by an Austrian institute . While originally, the system only covered chemical hazards, today it can additionally process a large variety of physical and ergonomic factors. Moreover, great improvements have been made in the processing and transmission of data, as well as the presentation and documentation of the results. PIMEX has become a fully developed and comprehensive system.
The flow of work is filmed with a video camera and synchronously the exposure data (vapour, dust, noise, etc) are recorded using direct-reading measuring instruments. The exposure data are added to the video film in form of graphs, bars or columns on the screen, by means of special software. The activity of the worker is linked at any time to the recorded exposure values.
The technical components that are needed to operate the system consist of:
- a direct reading sensor/meter (1) fixed to the worker, in the breathing zone (near mouth and nose) in the case of measuring chemical vapours;
- a datalogger/transducer (2) used to transfer the data to the computer.
- The system is complemented by the video camera and the notebook computer with the installed PIMEX software.
Figure 2: The components of the PIMEX-system:
- direct reading sensor/meter,
- digital video-camera,
- high-end notebook computer,
Making use of these PIMEX observations includes their presentation in training sessions.
A typical application of the system is the reduction of welding fumes generated by electro welding under different conditions. The welders are fitted with sensors near their mouths and noses in order to monitor those parts of the welding fumes which would actually enter the respiratory system. Their work processes are documented by video cameras, whereby processes and measured values are recorded and displayed on the notebook computer by means of the PIMEX software. The measurements are shown in three different forms: as digits, as bar graph and as a curve covering the whole process. The workers and other observers are thus in a position to relate the operations to the amounts of inhaled welding fumes, as displayed .
Often discussions between the workers and on-site experts start, resulting in repeated modification of
- the workflow,
- the type of extraction system,
- the positioning of the extraction system,
- the positioning of the welders themselves, including their working posture.
More general discussions can also be initiated: could it possible to use a less hazardous welding method such as TIG welding, or a more advanced welding machine such as a pulse current operated one. After the changes are implemented, the PIMEX observation can be started again and the records checked for improvements. This process continues until the workers and the on-site experts are satisfied of the exposure reduction achieved.
Table 1: Practical examples
|1||Car repair, solvent vapours and aerosols; reduction of exposure||Body parts in a car repair workshop were painted by means of hand-held spray guns. All workplaces were equipped with extraction systems and the workers were provided with personal protection equipment. Researchers conducted PIMEX observations with and without the extraction system in a typical paint booth and at a grinding workplace. Analysing the difference, it was proven that the extraction system worked efficiently. All exposure readings were below the threshold values. Little attention had been paid, however, to the cleaning of the spray guns at a washstand. Although the stand was fitted with an extractor, high exposure values were detected. The workers started experimenting with different extraction funnel positions and alternative work processes. Analysing the results with PIMEX led to a satisfactory exposure reduction within a short period of time .|
|2||Glass fibre reinforced plastic (GRP) application in waste water tanks, styrene; assessing where high exposures occur||Analysis of data from a spray booth in a plant producing waste water tanks in glass fibre reinforced polyester showed that more than half of the exposure was due to rolling with a metal roller. Exposure data were sorted according to the related step of the working procedure. With these data, each work step’s duration and relative importance to total exposure could be calculated Work involved in trimming off superfluous, partially hardened material made a large contribution to the total exposure. 46% of the total exposure occured in only 10% of the working time. A problem solving group designed and tested improvements and checked the efficacy of the implementation .|
|3||Furniture industry, wood dust; assessing when high exposures occur||The worker under study performed various manual carpentry tasks in a company which made specially designed interior fittings for offices, hotels and restaurants. The same analysis, as in the example above (waste water tanks), was performed and the result showed that working with a hand-held power tool (milling) made the greatest contribution to exposure. The sum of 48% of the total exposure was explained by 10% of working time .|
|4||Food production, dust; risk assessment and training||Dust from grains, milk powder etc. were measured and the data linked to the work process These dusts may not only cause explosions, but also allergic respiratory and skin diseases. Prevention measures were derived, implemented and their effectiveness checked. The recorded observations were used for training purposes. Safe behaviour improved considerably .|
|5||Schools, ergonomic furniture; ergonomic analysis and training||Conduction of comprehensive posture and movement analyses using sonometry (ultrasound) and PIMEX. Design recommendations were developed and the observations were used for training purposes, for example on how to adjust chairs and desks, and healthy sitting positions .|
|6||Paper industry; measuring heat and noise and strain on workers||PIMEX observations were used to analyse the effects of the work processes on the workers. Heat radiation, air humidity and temperature were recorded together with the heart rate. The individual strain could thus be determined. This was used to develop a workplace health promotion strategy .|
|7||Educational facilities; noise, and strain on teachers||Exemplary measurements were conducted during seminars, measuring noise in the seminar room and pulse of teachers and participants. Proposals on how the situation could be improved were discussed .|
Source: Overview by authors
The PIMEX system can also be used to support a change process in work places, utilising PIMEX videos as reflective material of the current situation .
PIMEX should not be used for compliance measurements to OELs, because the system uses direct reading instruments that are quite often non-specific for chemical agents and not adequately calibrated. PIMEX should be used when more detailed information about the exposure and its sources is needed.
PIMEX can be used in all sectors. While originally the system was restricted to air contaminants (see also: Monitoring, sampling and analysis of airborne dangerous substances), meanwhile any instrument that provides a signal that can be processed by the video mixer can be connected to the equipment . Research and development is still ongoing. The current scope of the system is presented in the following table.
Table 2: Scope of PIMEX applications
|Hazardous substances||- various types of dust, - fumes - aerosols, cooling lubricant mist, - organic solvents, - styrene, isocyanates, methyl methacrylate, - ammonia - nitrous oxide - carbon monoxide|
|Physical load||- noise, - heat-radiation, - vibrations, - electromagnetic fields|
|Ergonomic factors||- lighting, thermal comfort, air humidity, air movement/ wind velocity, - body postures, stress factors|
|Psychosocial factors/strain||- pulse, heart rate, heart rate variability, breathing rate, body temperature|
Source: adapted from , , 
Modern PIMEX systems are not restricted to record only one factor along with the video signal, but – as has been illustrated in some of the examples above – can process and record a number of measurements from different areas, such as for example heat radiation and body temperature or fumes, posture, electromagnetic fields and breathing rate.
Employers have to observe the legal requirements that are in the first instance laid down in the EU ‘OSH Framework’ Directive 89/391, adopted in 1989 : They have to ‘take the measures necessary for the safety and health protection of workers, including prevention of occupational risks and provision of information and training, as well as provision of the necessary organisation and means.’ (see also: OSH management and risk governance). A very important measure to comply with these requirements is the risk assessment that is compulsory in every company.
In an expert group discussion organised by EU-OSHA, PIMEX was regarded as an excellent tool to assist employers hereby .
The main advantage of the PIMEX method is that otherwise invisible risk factors can be visualised in real time. This allows the detection of otherwise hardly noticed risks or illustrates the danger of traditionally accepted risks. At the same time this can motivate the concerned workers to contribute to change the situation . As the PIMEX observation can instantly be replayed, experts and workers can identify exposure peaks and may analyse these work process steps together in detail and test different changes to work processes, movements or postures to reduce exposure. The effectiveness of the new measures can be tested by a new PIMEX observation. This can continue until a satisfactory reduction not only of the peaks but of the general level is achieved. Achievable reduction rates depend strongly on the type of process and usual former practices in the individual companies, however, exposure reduction rates of up to 90 % have been recorded . Best practice and bad practice can be illustrated for training purposes in order to show colleagues and newcomers how the work is performed best.
The solutions may cover all hierarchical levels of control measures:
- Elimination of hazards:
- The visualisation of the risks can trigger the search for elimination and substitution,
- Reduction of risks by technical measures:
- The positioning of the exhaust system nozzle, the adjustment of the machine in use etc. can be optimised using the PIMEX observation,
- Reduction of risks by organisational measures
- The work process can be optimised using the PIMEX observation,
- Reduction of risks by personal measures
- The application of PPE can be optimised using the PIMEX observation,
- Measures to implement safe working practices
- PIMEX can play an important part in behaviour based measures as it motivates workers to change their working practices sustainably and promotes a safety culture.
All types of measures need to be accompanied by training. Selected PIMEX observations provide excellent training material.
While the PIMEX method excels when measurable values are involved, application in accident prevention may be achieved by videotaping of work processes - without recording measured values. The latter method would only require a video camera and, in most cases, could be applied without external assistance. This method can also achieve a remarkable and lasting change in behaviour, as has been shown by Rupprecht  and would be much cheaper. However, since many accidents are not caused by a single factor but by a combination of factors, such as time pressure, stress, insufficient lighting, fatigue, etc, it could still be advisable to include measurements of situation related values, and to bear the higher costs and the complex handling of the PIMEX system, .
As has been mentioned above, PIMEX should not be used for compliance measurements to OELs, but only when more detailed information about the exposure and its sources is needed.
In some of the current versions of the PIMEX equipment extra data can be added afterwards: all measuring equipment able to save data continuously with a sound time interval (e.g. 1 s resolution) can be added to the recording afterwards.
Although the use of PIMEX is straightforward, the technical system is rather sophisticated. It is advisable to rent the system together with an expert, who can install it and give advice on its use. This makes PIMEX difficult to handle for SMEs. The expert group of the above mentioned EU-OSHA seminar suggest therefore sector solutions for SMEs. The relevant associations could use PIMEX to provide solutions to common problems in SMEs and make available recordings and observations as training material for their members .
The developers of the Dutch ‘Stoffenmanager’ (see also: Risk management tools for dangerous substances) have for example included PIMEX observations into their tool, to demonstrate the application of certain preventive measures .
Finally it should be mentioned that PIMEX is also an important tool for occupational hygiene research, for example on such topics as the connection between production parameters, work organisation and exposure, comparing protective systems or testing additional protective measures  (see also: OSH research).
PIMEX is a powerful tool that can effectively contribute to safety and health in companies. Research and development is still going on to improve the tool, its applications and scope: For example in 2011 two studies were published about research aiming at the visualisation of nanoparticles using PIMEX. The researchers of the first study monitored simultaneously both the personal exposure (in the breathing zone) and the background exposure. In this way the personal exposure to synthetic particles could be corrected for the background exposure to natural occurring nanoparticles or confounding factors . In the second study the possibility to combine PIMEX and measurement instruments for nanoparticles was tested. The researchers stated that some of these instruments are technically compatible with PIMEX .
In 2009 Hedlund and colleagues presented the Peak project, explaining their new approach to use PIMEX to complement epidemiological information on health effects. In the study, they assessed if there was a correlation between decline in lung function and working conditions in a fertilizer production plant in Norway. The aim was to identify peaks of work place exposure and use the data to refine questionnaires in follow up studies on lung function. Following fieldwork the research team also made several proposals on how to improve the PIMEX equipment .
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