Farhad Memarzadeh

Applications of ultraviolet germicidal irradiation disinfection in health care facilities: effective adjunct, but not stand-alone technology.

This review evaluates the applicability and relative contribution of ultraviolet germicidal irradiation (UVGI) to disinfection of air in health care facilities. A section addressing the use of UVGI for environmental surfaces is also included. The germicidal susceptibility of biologic agents is addressed, but with emphasis on application in health care facilities. The balance of scientific evidence indicates that UVGI should be considered as a disinfection application in a health care setting only in conjunction with other well-established elements, such as appropriate heating, ventilating, and air-conditioning (HVAC) systems; dynamic removal of contaminants from the air; and preventive maintenance in combination with through cleaning of the care environment. We conclude that although UVGI is microbiocidal, it is not “ready for prime time” as a primary intervention to kill or inactivate infectious microorganisms; rather, it should be considered an adjunct. Other factors, such as careful design of the built environment, installation and effective operation of the HVAC system, and a high level of attention to traditional cleaning and disinfection, must be assessed before a health care facility can decide to rely solely on UVGI to meet indoor air quality requirements for health care facilities. More targeted and multiparameter studies are needed to evaluate the efficacy, safety, and incremental benefit of UVGI for mitigating reservoirs of microorganisms and ultimately preventing cross-transmission of pathogens that lead to health care-associated infections.

Role of air changes per hour (ACH) in possible transmission of airborne infections

The cost of nosocomial infections in the United States is estimated to be

Energy Efficient Laboratory Design: A Novel Approach to Improve Indoor Air Quality and Thermal Comfort

4 billion to

The Effects of Patient Movement on Particles Dispersed by Coughing in an Indoor Environment

5 billion annually. Applying a scientifically based analysis to disease transmission and performing a site specific risk analysis to determine the design of the ventilation system can provide real and long term cost savings. Using a scientific approach and convincing data, this paper hypothetically illustrates how a ventilation system design can be optimized to potentially reduce infection risk to occupants in an isolation room based on a thorough risk assessment without necessarily increasing ventilation airflow rate. A computational fluid dynamics (CFD) analysis was performed to examine the transport mechanism, particle path and a suggested control strategy for reducing airborne infectious disease agents. Most studies on the transmission of infectious disease particles have concentrated primarily on air changes per hour (ACH) and how ACH provides a dilution factor for possible infectious agents. Although increasing ventilation airflow rate does dilute concentrations better when the contaminant source is constant, it does not increase ventilation effectiveness. Furthermore, an extensive literature review indicates that not every exposure to an infectious agent will necessarily cause a recipient infection. The results of this study suggest a hypothesis that in an enclosed and mechanically ventilated room (e.g., an isolation room), the dominant factor that affects the transmission and control of contaminants is the path between the contaminant source and exhaust. Contaminants are better controlled when this path is uninterrupted by an air stream. This study illustrates that the ventilation system design, i.e., when it conforms with the hypothesized path principle, may be a more important factor than flow rate (i.e., ACH). A secondary factor includes the distance from the contaminant source. This study provides evidence and supports previous studies that moving away from the patient generally reduces the infection risk in a transient (coughing) situation, although the effect is more pronounced under higher flow rate. It is noted that future research is needed to determine the exact mode of transmission for most recently identified organisms.

ANSI/ASSE Z9.14 “Testing and Performance Verification Methodologies for Ventilation Systems for Biological Safety Level 3 (BSL-3) and Animal Biological Safety Level 3 (ABSL-3) Laboratories” Leads Standard Development for High-Containment Laboratory Performance:

The requirements of laboratory facilities differ dramatically from those of other buildings. As we expand our biocontainment needs to Biosafety Levels (BSL) -2, -3, and -4, a clear need exists for an air quality and thermal comfort initiative targeting these facilities. The thermal comfort of occupants in laboratories can be controlled by the choice of ventilation strategy. Added benefits are the realization of a significant energy savings and improved indoor air quality. This study employs an advanced numerical simulation and empirical validation to assess the performance of active chilled beams in a general laboratory layout having some equipment intensive areas. The study examines the removal effectiveness of gases and airborne particles in such a system. Chilled beam performance is also compared to a ceiling diffuser system with and without cooling panels. The results of this study show that chilled beams improve thermal comfort and can be operated at reduced Air Changes per Hour (ACH) while maintaining a comfortable environment in occupied zones expressed as the Predicted Percentage Dissatisfied (PPD). To obtain a similar level of thermal comfort, a higher ACH is required in a ceiling diffuser system with cooling panels and bench exhausts. The chilled beam system also improves the removal effectiveness of gases or airborne particles because of the inherent better mixing in the room compared with the use of ceiling diffusers. In the cases studied, chilled beams have an insignificant effect on the fume hood containment. As satisfactory thermal comfort and air quality was achieved at a lower flow rate when compared with an all-air ceiling diffuser system, a savings of around 22% is estimated in annual energy costs for cooling and ventilating a typical lab in the Washington, DC area. The methodology and results of this study may be applied to further research for other laboratory types, or climatic conditions than those proposed in this study.

Numerical Investigation on Ventilation Strategy for Laboratories: An Approach to Control Thermal Comfort and Air Quality Using Active Chilled Beams

This study investigates the influence of a moving patient on the transport characteristics of coughing particles by dynamic meshing and the Lagrangian particle tracking method. Through simulation, particle movement during the initial coughing, patient movement, and stationary flow phases was examined. Two different particle sizes (5 μm and 10 μm) were used and yielded small differences in the initial airflow after coughing. During the patient-moving phase, the temporal particle distribution in the upper, breathing, lower, and near-floor zones were simulated. The amplified air-velocity field induced by the moving patient enhanced the particle entrainment, thus increasing the risk of contamination (defined as particle system entropy) in the whole room. Both temporal and final particle distribution during the stationary flow phase were studied. Walking speed affected the particle distribution in the traveling direction, but not in the vertical or lateral directions at the end of the simulation. Turbulence dispersion played a critical role in the spread of the particles through the coughing and patient-moving phases.

Comparison of Operating Room Ventilation Systems in the Protection of the Surgical Site

A February 2013 Government Accounting Office (GAO) letter to Congress, titled “High-Containment Laboratories: Assessment of the Nations Need Is Missing,” (GAO, 2013) reiterates the concern in the 2009 GAO report (GAO, 2009) that there is still a need to “develop, in consultation with the scientific community, national standards for the design, construction, commissioning, and operation of high-containment laboratories, specifically including provisions for long-term maintenance.” With more high-containment laboratories coming online, the level of overall risk when laboratory accidents occur is unknown (GAO, 2013).

Reducing risks of surgery

Laboratories are usually equipment intensive. The supply flow rates required to cool these laboratories are generally higher than in a less equipment intensive zone of the building. The thermal comfort of occupants in laboratories can be controlled by the choice of ventilation strategy. This study employs Computational Fluid Dynamics (CFD) simulation to assess the performance of active chilled beams in a general laboratory layout with some equipment intensive areas and the removal effectiveness of such a system. The chilled beam performance is also compared with at of ceiling diffusers. The results from this study show that the chilled beams improve thermal comfort, and they can be operated at as low as 4 ACH while maintaining very satisfactory average PPD (around 10%) in the occupied zones. The chilled beam system also improves removal effectiveness because of the inherent higher total supply flow rate that results in a better mixing in the room than ceiling diffusers. The chilled beams in the cases studied are seen to have an insignificant effect on the hood containment. As satisfactory thermal comfort and air quality can be achieved at a lower flow rate in comparison with all-air ceiling diffusers, a 14% saving is estimated in annual energy cost for cooling and ventilating a typical lab in the Washington DC area.Copyright