ASHRAE Journal - May 2020 - 22

TECHNICAL FEATURE

and a comparison of contaminant purging performance
of different ventilation strategies. Results showed that
relative pressurization is very sensitive to door airtightness and that the use of poorly fitted doors may fail to
comply with the pressurization criteria. Manual calculations would be impractical for these analyses, given a
large number of interconnected zones.
The CFD analysis demonstrated that the use of unidirectional flow diffusers reduces the cross-contamination
risk on the surgical site due to the door-opening and
personnel movement transport when compared to the
use of mixed ventilation for the studied case. Design
improvements may apply a supplemental ceiling
exhaust that would enhance the contaminant purging
capability. The parametric tests of discharge velocity on
purging performance demonstrated that the contaminant transport from the surrounding air to the region
of the operation table due to entrainment flow is highly
dependent on the Archimedes number (Ar).
The detailed room flow field results wouldn't be available without the coupled CFD detailed calculation, due

to the "well-mixing" assumption of multizone models.
The software simulations reproduce the basic performance of the well-known techniques relating to room
pressurization and ventilation strategies, indicating that
it may be a suitable design and analysis tool for studying ventilation solutions in health-care applications.
Therefore, the use of coupled CFD-multizone models
may be a significant tool for studying different arrangements early in the design process to produce additional
information that may improve the design solution.
SSI risk mitigation in OR is a multidisciplinary task,
involving several professionals. Besides ventilation,
several other factors affect this task, such as the stringent application of protocols, surface disinfection, and
patient care product sterilization, among others. The
main objective for the ventilation analysis performed in
this article was not to present a solution that mitigates
SSI risk in ORs, but rather to demonstrate the applicability of simulation software that may be a relevant
tool for studying ventilation parameters in health-care
applications.
Some limitations arise from the use of the basic modeling, fitted to conceptual analysis in early design phases.
Additional simulations, with further model enhancement, may be used for the selected solutions to provide a
more detailed result of the solution's performance.
Other contaminant sources inside the OR are relevant,
like the staff and he patient. Contaminant migration
through door opening depends on several factors,
including the opening frequency and corridor contaminant concentration. Experimental tests of this contaminant migration have proven to be difficult, and more
research is needed on this topic. On the other hand, the
use of numerical simulations may be used for parametric tests and to study the effect of isolated contributors.
This article focused on the contribution of the doors,
to demonstrate the applicability of CONTAM-CFD software for similar simulations. Future work will study the
effects of staff and patient contributions.

References
1. Spagnolo, A.M., G. Ottria, D. Amicizia, F. Perdelli, M.L.
Cristina. 2013. "Operating theatre quality and prevention of
surgical site infections." Journal of Preventive Medicine and Hygiene
54(3):131-137.
2. ANSI/ASHRAE/ASHE Standard 170-2017, Ventilation of Health
Care Facilities.
3. ANSI/ASHRAE Standard 62.1-2016, Ventilation for Acceptable
Indoor Air Quality.
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ASHRAE Journal - May 2020

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