EOLIOS carries out the design pre-qualification and the containment tests of your fume hoods through CFD simulation: SF6 tracer-gas containment, front air velocity and compliance with EN 14175 / XP X 15-203 standards.
The laboratory fume hood is a localised protection system used wherever hazardous substances are handled. Its mission: to limit the exposure of people by capturing and extracting the toxic vapours and volatile dust generated within its enclosure, through an air-extraction flow. To guarantee that their performance is maintained over time, fume hoods are subject to periodic checks.
EOLIOS carries out the design pre-qualifications and the containment tests: contamination control, dispersion of pollutants and gases, study of critical failure scenarios, identification of bypass and recirculation airflows, sizing of the grille layout and optimisation of the setpoints.
The assessment of fume-hood operation is subject to the European standard EN 14175, which details the performance-assessment methodology during qualification, acceptance or routine tests. During a check, front air-velocity tests are carried out by hot-wire anemometry, an SF6 tracer-gas containment test is performed, as well as a qualitative smoke flow visualisation.
In France, for fume hoods installed before 2006, the checks had to comply with the XP X 15-203 standard, which set in particular:
The EN 14175 standard considerably widens the number of tested parameters. The threshold values:
The mandatory checks concern the extracted air flow rate (measured in the extraction duct) and the front air velocity (by thermal anemometry), whose values serve as a reference for future periodic checks.
The principle of the SF6 gas containment test:
For the NF EN 14175 standard, the number of measurement points depends on the width of the fume hood (part 3 of the standard); during the tests, the movable sash is opened to 500 mm.
The simulations contribute to a better overall understanding of the thermo-airflow phenomena and to the development of relevant technical solutions from the design stage. Laboratories can be simulated in their entirety, allowing the simultaneous analysis of the impact of numerous phenomena. The CFD qualification study notably highlights the presence of parasitic airflows disturbing the entrance of the fume hoods.
At the start of design, multiplying experimental prototypes is costly and time-consuming. CFD simulation makes it possible to assess a large number of prototypes in a limited time, to optimise the systems and the placement of the fume hoods. It gives access to parameters that are difficult to measure experimentally — data at every point and not localised — to precisely identify the containment leaks. Integrating CFD into one's protocols means securing and accelerating the qualification.
To carry out an instantaneous spatial measurement of the air velocity, we use precision fluid mechanics. The flows are governed by the Navier-Stokes equations; analytically insoluble, they are solved numerically by the finite element method, which provides the closest solution to the physical problem. The inlet and outlet conditions — supply, extract and fume-hood extraction flow rates — are posed as assumptions and must be verified to validate the conclusions.
During qualification, it is imperative to control the leakage rate of the polluting agents so as not to contaminate the user. To model this polluting agent, we simulate a tracer gas according to different methods in order to guarantee fine precision and reliable results.
To check the compliance of the containment with the standard, we model the diffusion of the tracer in the fume hood in steady state. An iso-volume method then makes it possible to check that all the tracer is indeed contained within the enclosure at the regulatory scale. If the result is verified, the fume hood meets the containment conditions imposed by the legislation.
The numerical fume-hood qualification by CFD reproduces the tracer-gas containment test and the front air-velocity analysis, visualising the parasitic flows and the tracer diffusion. This approach provides data at every point of the volume, secures compliance with the EN 14175 / XP X 15-206 standards and accelerates the design as well as the acceptance of the fume hoods.
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