ESI Group valide les compétences de Rensair en fourniture d’air pur

avril 4, 2022 – 5 Min

Le débit d’air est un facteur essentiel pour les performances des purificateurs d’air Portatifs et constitue un point de différenciation (souvent dissimulé) entre les concurrents sur le marché. Réussir à purifier l’air de toute une pièce est un véritable défi d’ingénierie. Les arguments commerciaux de nombreux fournisseurs de purificateurs d’air sont souvent non fondés. Certains ne font guère plus que purifier plusieurs fois le même air situé autour de l’appareil lui-même, ce qui ne limite pas les risques d’infection par des agents pathogènes et expose les clients ne se doutant de rien, les laissant sans aucune protection. Les acheteurs devraient toujours chercher à savoir si les arguments commerciaux sont corroborés par des tests effectués par des laboratoires de recherche indépendants et respectés et des centres de test indépendants.  

Au 1er trimestre 2022, Rensair a chargé ESI Group d’effectuer des tests approfondis concernant le crucial débit d’air du purificateur d’air Portatif HEPA/UVC de qualité hospitalière Rensair. ESI Group est un pionnier et un leader mondial de la modélisation prédictive de la physique et du prototypage virtuel. Créée en 1973 et basée en La France, cette société a pour mission première de simuler le comportement des produits au cours de tests et d’évaluer l’impact de l’environnement sur les performances des produits.

L’étude d’ESI comprenait à la fois des tests de dynamique des fluides computationnelle (Partie 1) et une modélisation in situ dans une salle de chirurgie dentaire de l’hôpital de Birmingham (Partie 2).

Phase 1: Characterisation of flow through the unit

After confirming that the airflow rate on high and low settings was actually commensurate with the manufacturer’s claims (560 and 300 m3/h respectively), ESI conducted divers tests on the direction and uniformity of the intake of dirty air and outflow of air pur.   The tests augmentation de 23% des cas de COVID-19 chez les élèves hemispherical intake of dirty air from above and around the circumference of the unit, sucking in at 360 degrees regardless of the angle of the unit. Uniform pressure and velocity were recorded inside the filter drum, with no air escaping back up through the unit. The downward pressure forces air through the Filtre HEPA evenly, avoiding premature wear.

Uniform intake downward pressure through the filter

The tests also demonstrated an even distribution of outflowing air. This resulted in the conclusion that the Rensair device provides circumferentially and axially uniform air pur delivery at the lowest (300m3/h) and highest flow rates (560m3/h).

Even 360 degree distribution of air pur

The next phase of testing analysed the outflow from the lower part of the unit and the subsequent air pur distribution throughout the room.  The unit quickly propagations purified air at 360 degrees in a uniform, outward ‘radial jet’ motion parallel with the floor. This enhances room penetration and encourages vortex circulation of airflow throughout the space, such that air pur bounces off the walls, then the ceiling and then back into the entire room. Importantly, the vortex flow pressures particles and aérosols downwards, a key benefit  during AGPs.

Radial jet motion travels parallel with the floor and bounces of walls and ceiling

Phase 2: Dental Treatment Room – Birmingham Hospital

The in-situ modélisation comprised a large dentaire treatment room (44.7m3, , une salle de cabinet dentaire faisant en général environ 30 m3) with three occupants and an integrated ventilation system delivering 5 air changes per hour (ACH), which under current UK guidance would require the maximum jachère period of 30 minutes.

On the high fan speed setting, which is generally recommended during AGPs, and with the Rensair unit supplementing the existing 5 ACH ventilation, the average age of air in the room stabilised at 158 seconds, with an air change rate of 17.6 and circulation efficiency of 65%. ESI concluded that ”When used in isolation, or with the treatment room’s mechanical ventilation notionally turned on, the air circulation efficiency scales with ACH irrespective of installation location; and rates well in comparison with other commercial Portatif and wall-mounted units of similar capacity.”

Average age of air with and without 5 ACH ventilation

Clearance – defined as a 99% reduction (log 2 reduction) of particles emanating from the patient – was logged at just 0.84 of a minute when combined with the existing 5 ACH. With the ventilation system turned off, the Rensair unit alone achieved clearance in 1.3 minutes on the high setting, with an ACH of 12.6. Evidence that a Rensair unit on its own can achieve 99% reduction in 1.3 minutes gives confidence that only the minimal jachère time is required between patients, thereby allowing pre-pandemic ways of operating and maximising patient throughput. Healthcare professionals should be encouraged to seek such validated performance data when comparing air purifiers.

Post AGP particle clearance time

Of critical importance is that deposition and near patient flow field tests demonstrated high-to-low particle precipitation, drawing aérosols downwards from the AGP source and away from the dentist’s head, thereby providing protection from infectious particles. This occurred irrespective of the position of the Rensair unit in the room.

AGP source particle precipitation without the Rensair unit
AGP source particle precipitation with the Rensair unit

Conclusion and key résultats

Key résultats are:

  • Rensair device stimulates a ventilation pattern corresponding to TOROIDAL.
  • Rensair device in-situ demonstrates precipitation of aérosols from AGPs.
  • Rensair device demonstrates a stable floor-wise room penetration, avoiding ground particulates (dust/carpet) ingestion into the device which may prematurely block the filter. 
  • Rensair device achieves rapid post AGP clearance ie. 99% reduction (log 2 reduction) of particles emanating from the patient.

Airflow is critical to the effective performance of air purifiers, regardless of the technologie used to trap and/or inactivate les agents pathogènes;. To successfully clean all the air in a room requires a combination of quality components (e.g. strong fan) and smart engineering (e.g. not creating exhaling drafts). Given the health risks at stake, manufacturers’ claims should not be taken at face value, but supported by 3rd party independent tests that show whether a unit is truly capable of cleaning all the air in a room, and in a decent sized room (rather than a small test chamber).

The ESI Group study unequivocally proves the efficacy of Rensair’s air purifier. Rensair’s robust centrifugal fan creates high, uniform static pressure in the cylinder et uneces air effectively out through the dense Filtre HEPA, travelling across the floor and enhancing the penetration of air pur throughout the entire space.

ACH AGP Air changes per hour Air purification Air purifier clean air Clean Air Delivery computational dental practice Dentists efficacy ESI fluid dunamics hepa13 hospital grade in-situ modelling inflow outflow Rensair toroidal treatment room uvc ventilation

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