Evaluation of WellAir’s FDA-Cleared Defend 400 in hospital operating room

F. Soberon & L. Lawlor
Hospital - Operating Room; Glen Echo, Maryland
Full Report


Testing Location

One healthcare facility, one environment within the facility: operating room located in Glen Echo, Maryland, Washington DC.

The testing was performed over 6 days in December 2021, March 2022 and April 2022. There were 3 days for testing and 3 days for control sampling; with one day each on each month listed.

Product Background

The FDA has cleared the Defend 400 (NV 400) as a 510(k) Class II Medical Device to filter out and inactivate airborne viruses and bacteria for medical purposes within small to medium-sized rooms. 

The NV 400 uses NanoStrike™ Technology combined with a triple-stage Camfil® filter system to provide a combined solution for air disinfection and particle removal. It inactivates aerosolized viruses, bacteria, and fungi and purifies the air of pollen, particulate matter (PM), volatile organic compounds (VOCs), and odors. 

The device is a free-standing, portable recirculating air cleaning system designed for continuous 24/7 front-line protection in healthcare settings to provide airborne infection control where the risk of Healthcare-Associated Infections (HAIs) and Surgical Site Infections (SSIs) are at their highest.

The NV 400 is UL 2998 and CARB validated for zero ozone and UL 867 safety certified.


To test the hypothesis that the use of a portable stand-alone air cleaner in an operating room within a hospital/healthcare environment is effective in reducing airborne bioburden in the environment.


The levels of airborne bioburden were measured by collecting 100 litre air samples on TSA agar plates using an impaction air sampler.

An equal number of test and control samples were taken on the different days. Samples were taken in duplicate. Test and control samples were collected over 3 days each, 6 in total. A total of 120 air samples were collected: 60 during controls sampling, and 60 during test sampling. The air samples were analysed by EMSL lab for bacterial counts and identification of three most prominent species present in each agar plate.

The Defend 400 device was set at speed 5 (maximum speed), 210 CFM (356 m3/h) and was switched on for the duration of the test sampling periods. The device was turned off for the duration of the control sampling periods.

Summary of Results

Post-operation total colony counts saw a reduction of 56.7% between control and test samples (p-value 0.003432). 

A total of 41 different bacterial species were identified in the agar plates analysis that were collected throughout the trial. Identification of 1 bacterial pathogen and 19 bacterial opportunistic pathogens.

    Conclusion and Discussion

    The use of a portable stand-alone air cleaner in an operating room has shown substantial reduction in airborne bacterial bioburden overall. Read the one page summary here.

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