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Patient rooms in healthcare establishments are prone to contamination by various pathogens. These pathogens can spread and survive on various surfaces, and represent potential risks of causing healthcare-associated infections (HAIs). A recent study from Hamburg, Germany evaluated the efficacy of two automated room disinfection (ARD) devices to address surface disinfection in real-life conditions.

The Institute for Medical Microbiology, Virology, and Hygiene at the Medical Center Hamburg-Eppendorf conducted testing in order to evaluate the effectiveness of two automated room disinfection devices. An aerosolized hydrogen peroxide (aHP) device (Sentinel H2O2 Fogger, Germany) and a gaseous ozone-based device (STERISAFE PRO, Denmark), were tested under real-life conditions to assess their effectiveness. The two devices were tested in a patient room of 45 m2 which included a bathroom and anteroom.

The ability to disinfect surfaces was evaluated based on the bacterium Enterococcus faecium.  E. faecium can be both naturally present in the gastrointestinal tract of humans and animals, and pathogenic (e.g. neonatal meningitis, endocarditis, urinary tract infections). The vancomycin-resistant E. faecium is known as Vancomycin-resistant Enterococcus (VRE).


Two types of contamination levels were introduced for this experiment:

Test (1) high primary contaminated surfaces (HCS), corresponding to 107-108 cfu load;

Test (2) secondary contaminated surfaces (SCS), corresponding to 102-103 cfu load.


Test (1) served to prove manufacturer disinfecting claims (log10 reduction, LR > 5), while Test (2) represented realistic bioburden. Samples were positioned vertically and horizontally, and at different heights. 22 HCS samples and 4 SCS samples were introduced in total

Both automated systems were operated following manufacturer’s instructions. For the STERISAFE PRO, this meant achieving an ozone concentration within 70-80 ppm, with 15 min holding time and 80-90 % relative humidity (%RH); the total time of disinfection was approximately 3 hours.

For the Sentinel Fogger, the fogging was first set at 20 minutes as per the manufacturer’s instructions. However, due to unsatisfactory efficacy results, this fogging time was increased to 30 min. For both runs, the total disinfection time was approximately 2 hours.


Both devices achieved complete bacterial elimination on realistically contaminated surfaces (SCS samples, LR > 3). However, only the STERISAFE PRO showed full efficacy for highly contaminated surfaces (HCS, LR > 5) when following the manufacturer’s instructions. The Sentinel Fogger only achieved an average of 2 LR for HCS samples with a fogging time of 20 min, with different results depending on the samples’ positioning (1.73 LR main room, 2.31 LR anteroom, 1.86 LR bathroom). Only when going above manufacturer’s recommendations (fogging = 30 min) the system managed to reach full efficacy (LR > 5).


Both devices were suitable for achieving activity on a realistic bioburden under their respective manufacturer’s instructions. However, under these conditions, only the STERISAFE PRO met the requirement for a bactericidal effect, while the Sentinel aHP fogger needed extra time and biocidal material to achieve the same effect.

The authors highlighted the following limitations of their study:

    • Only one pathogen tested;
    • Absence of soiling/organic load;
    • Only one surface material was tested (ceramic tiles).

Occupational safety aspects are well-taken in account with the STERISAFE PRO (…). In contrast, there is no possibility of monitoring or logging process parameters for a simple aHP nebulizer. For such device, it is recommended to use additional measurement equipment to verify sufficient concentration and ensure adherence to safety exposure limits afterwards.

Read the full article here


Knobling B., Franke G., Klupp E.M., Belmar Campos C. & Knobloch J.K. (2021). Evaluation of the Effectiveness of Two Automated Room Decontamination Devices Under Real-Life Conditions. Frontiers in Public Health 9: 1-7. doi: 10.3389/fpubh.2021.618263