FM Articles

Saving Lives and Saving Energy With Advanced Airflow Controls


When it comes to hospitals, what aspect of the physical plant links the numbers 20,800 and 13,600?

Here’s a hint: $20,800 is the approximate cost per case of surgical site infections (SSIs) according to the Center for Disease Dynamics, Economics and Policy (CDDEP), while $13,600 is the rough energy cost per bed in a typical 200,000 square foot U.S. hospital per the E Source Companies.

While hospitals are complex environments with many facilities and human factors contributing to patient outcomes and operating costs, one system that effects both the SSI and energy cost numbers is the ventilation airflow controls.

As patient wellness is job one, many hospitals take a conservative approach to keeping their indoor air healthy in order to meet Joint Commission standards. Yet, with today’s airflow control technologies, facility owners and operators do not need to make an either/or choice between patient safety and reducing energy costs.

Role of Airflow Controls in Patient Health
Control of airborne pathogens is important in virtually all hospital areas, but especially so in operating rooms, endoscopy rooms and patient isolation rooms – places where patients are most vulnerable to acquiring infections.

As discussed at length in the Joint Commission Perspectives newsletter, November 2014, additional hospital areas in which airflow control is crucial include delivery rooms when patients have airborne communicable diseases, protective environment rooms and special procedure rooms. Important functions of the ventilation system in all of these spaces include providing appropriate pressure relationships, air exchange rates and air filtration of airborne contaminants ranging from dust to fumes, gases and biological agents.

Reducing SSIs is critical, as patients who acquire one incur approximately 7 – 10 additional hospital days following surgery, and are at a 2 – 11 times higher risk of death, according to researchers at the University of Genoa. The researchers note that “maintaining a high quality of the air in the operating theatre is essential to controlling the risk of surgical infections.” Further, reducing the risk of SSIs requires an airflow system that provides “ventilation (dilution), air distribution, room pressurization (infiltration barrier) and filtration (contaminant removal).”

Impact of Airflow Controls on Facility Costs
Energy represent 51% of hospital facilities costs, according to a 2014 survey by the American Society of Healthcare Engineers (ASHE). Given that space heating is the single largest source of natural gas use in hospitals and that ventilation ranks second only to lighting for electricity use, paying attention to the airflow systems can pay big energy dividends.

“With the advent of new technology, many organizations are dynamically controlling their HVAC systems to respond to facility demand while still providing a protective environment for patients and staff,” writes Dick Moeller in the August 2014 issue of Joint Commission Perspectives. “Similarly, organizations are now allowed and even encouraged to take advantage of technology to reduce total airflows during periods of nonuse for energy efficiency in critical spaces within a hospital, such as operating rooms.” Although total airflow reduction is permitted in these instances, temperature, humidity and pressure differentials with surrounding areas must be maintained per code.

Airflow Control Problems
Beyond energy costs, the ventilation system also effects maintenance costs. Hospital facility managers often find that their pressurized spaces – such as operating rooms and patient isolation rooms – do not function as designed. Notably, poor airflow control can reduce patient safety and waste energy. Common causes of poor airflow control include:

  • Installation issues caused by duct runs that are not as straight or as long as required
  • Slow speed of system response due to measuring delays
  • Instability due to pressure variation
  • Sensor drift requiring frequent recalibration
  • Unbalanced airflow demanding additional balancing / commissioning work
  • Clogging of sensors, necessitating periodic maintenance

It is important to note, “A dynamic system can introduce risk if not monitored closely,” writes Dick Moeller. “Consequently, there is a need to recognize and compensate for the effect of changing pressure differentials in different locations.”

Improperly maintained systems or old technologies can cause change in pressure relationships and raise the cost of operation in a healthcare facility for service, repair as well as costs associated with infection risk.

For example, in a facility with 500 traditional VAV terminal boxes, annual cleaning costs are on the order of $50,000 – $100,000. Associated with these costs are also the time involved by staff in regards to infection control risk assessments (ICRA) and reporting. In contrast, choosing advanced airflow controls with high reliability can help reduce such costs, as well as ensure minimal downtime and disruption to hospital activities.

The negative impact of SSIs is so significant that Joint Commission accreditation of hospitals includes critical evaluations of number of SSIs, and equipment inspection, testing and maintenance (ITM) practices. As of January 1, 2017, every observation will be a finding, and every finding will require evidence of standards compliance (ESC) within 60 days of a survey. Even single observation findings will require an ESC.

Advanced Airflow Controls in Brief
In contrast to traditional variable air volume (VAV) terminal boxes often used in HVAC systems for commercial and institutional buildings, hospital facility managers are realizing numerous benefits from airflow control systems using venturi valves.

Such valves provide hospitals with a more accurate airflow control solution that allows them to safely maintain their pressurized spaces while reducing their energy costs. Pressure-independent flow metering venturi valves, such as those from Phoenix Controls, provide high accuracy airflow control due to:

  • Using flow metering technology that does not need long duct runs
  • Having a one second response speed, which valves requiring flow measurement cannot match due to inherent signal latency between flow sensor, controller and actuator
  • Relying on a cone assembly that maintains flow with changes in static pressure, so that air delivery rate is not compromised when static pressure changes

Advanced valves allow higher turndown ratios than traditional VAV terminal boxes – up to 20:1 versus 3:1. This means the device has a wider range over which it can accurately measure airflow. With this improved accuracy, a hospital can save energy with lower air volume, while not compromising room pressurization. This is especially important in operating rooms that use high airflow and more outdoor air, which requires energy to be conditioned.

Additionally, valves without flow sensors or dampers eliminate the cost of regular cleaning of such items, which reduces maintenance costs.

As with traditional VAV terminal boxes, venturi valves can be integrated into the building automation system (BAS) via BACnet capability.

Case study – University of Florida Health at Gainesville
As part of an overall strategy to better manage its facilities for patient comfort and energy management, UF Health at its Gainesville hospital retrofitted 23 operating rooms with advanced venturi valves linked to the existing BAS.

Prior to the upgrade, accurate airflow monitoring by the BAS was hampered by lint buildup on the flow rings in the exhaust and return air terminals. The risk was that if more air got pulled out than brought in, negative pressure would be created in the ORs, potentially allowing infiltration of airborne pathogens.

Each retrofitted OR now has a pair of variable air volume venturi valves with an occupancy sensor. The operating rooms are set at 20 air changes per hour (ACH) in the occupied mode and turned down to the minimum flows required to maintain the required unoccupied room pressure, which ensures safety while helping contribute to a 32% reduction in energy use.

In addition to the Joint Commission’s equipment inspection, testing and maintenance (ITM) practices, the Centers for Disease Control & Prevention (CDC) outlines comprehensive recommendations for air handling in its “Guidelines for Environmental Infection Control in Health-Care Facilities.” CDC’s criteria address air pressure, air changes per hour (ACH), and humidity controls, among other factors. Today’s advanced airflow controls can help meet these healthcare criteria, while also helping hospitals save on their ever-increasing energy costs.

Cheryl Laniewicz is the sales manager for healthcare at Phoenix Controls, a leading manufacturer of precision airflow control systems for critical room environments. Her background includes 12 years of HVAC industry experience, and over 20 years of technical sales and specification design assist experience in the healthcare, laboratory and research industries.

 Dave Rausch is the market manager for Phoenix Controls. He has more than 20 years of experience in the building industry, including engineering and product management roles in airflow controls and fire suppression systems.

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