Rensair air purifier test achieves post AGP clearance in 1.3 minutes

April 5, 2022 – 2 Min

In-situ modelling tests conducted by ESI Group in a hospital dental treatment room have demonstrated that Rensair’s portable, hospital-grade air purifier can achieve clearance in just 1.3 minutes, delivering an air change rate of 12.6 Air Changes per Hour (ACH) when used with no supplementary ventilation.

Rapid ‘clearance’ – defined as a 99% reduction (log 2 reduction) of particles emanating from the patient – means that only the minimal fallow time is required between patients, thereby enabling pre-pandemic ways of operating and maximum patient throughput.

The UK government’s January 17 2022 updated guidelines on post AGP downtime for dental practices state that, where there are 10 or more ACH, a baseline post AGP downtime of 15 minutes is recommended. However, that downtime increases to 20 minutes where there are 6 to 9 ACH and to 30 minutes where there are 1 to 5 ACH or where the ventilation rate is unknown.

ESI Group – experts in predictive physics modelling, virtual prototyping and simulation of  product behaviour – conducted the tests on the Rensair unit in a large dental treatment room (44.7m3, compared to a typical dental practice room at circa 30m3) with three occupants and an integrated ventilation system delivering just 5 ACH.

ESI concluded that “When used in isolation, or with the treatment room’s mechanical ventilation notionally turned on, the (Rensair device’s) air circulation efficiency scales with ACH irrespective of installation location; and rates well in comparison with other commercial portable and wall-mounted units of similar capacity.”

“The existing 5 ACH ventilation demanded the maximum fallow period”, said Christian Hendriksen, Co-founder and CEO at Rensair. ”With the Renair unit switched on in addition to 5 ACH, clearance was logged at just 0.84 of a minute. The Rensair unit alone, when we switched off the existing HVAC system, achieved 1.3 minutes clearance. Either way, the end result is to shift from maximum to minimum post AGP downtime.”

ESI also analysed the outflow of clean air from the Rensair unit and its subsequent distribution throughout the room. The unit quickly spread purified air at 360 degrees in a uniform, outward ‘radial jet’ motion parallel with the floor. This enhances room penetration and encourages toroidal circulation of airflow throughout the space, such that clean air bounces off the walls, then the ceiling and then back into the entire room. Importantly, the toroidal flow pressures particles and aerosols downwards, drawing them away from the AGP source and from the dentist’s head, thereby providing protection from infectious particles.

“Dental practices should seek evidence of credible, third party testing before specifying air purification units”, added Hendriksen. “Airflow is critical to performance, but many manufacturers fail to substantiate air circulation claims and do not have the engineering know-how to clean an entire room.”

The full ESI Group report is available on request. Please email

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