Pandemic-Ready HVAC Systems

A i rf lo w C o n t ro ls O f fe re d b y PANDEMIC READY HVAC systems for worst-case scenarios

by Michael Soper

he term “infection control” is usually associated with the day-to-day practices of hand sanitation, disin- fecting surfaces, wearing clean gar- Tments and monitoring the risk of cross- contamination between patients. However, the term can also pertain to pandemic influenza. A pandemic can occur when a strain of the influenza virus mutates into a form not easily handled by the human immune system and is re- sistant to treatment with known med- ications. Most viruses of this type are highly contagious and will spread easily and rapidly throughout the global popu- lation. Influenza viruses have threat- ened the globe at least three times in known history and there is a widely held N

O belief among scientists that a new pan- I T

A demic is inevitable. R O

P Considerable planning has been de- R

O voted to pandemic preparedness at the C

L state and federal levels. However, facili- O R

T ties at the local level are thought to be N

O unprepared to implement these plans. C

I There would be inadequate staff, sup- N E plies would quickly run low and there O H P

would not be enough isolation rooms for Y S

E contagious patients. T

R According to the Occupational Safety U O

C and Health Administration (OSHA),

T “the National Strategy for Pandemic In- O H

P fluenza calls for communities to antici-

Tracking pairs of patient room venturi valves, which are used for room-level, pandemic-ready HVAC systems. Pandemic ready

LEFT Constant-volume valves with damper-controlled recirculation or exhaust. RIGHT Multiple VAV shutoff valves controlling recirculation or exhaust. pate large-scale augmentation of exist- ing Engineers publications that prevent surization is critical, especially to contain ing health care facilities.” the use of patient rooms as AII rooms in dangerous airborne pathogens. Furthermore, airborne precautions an emergency. In fact, several U.S. hospi- Zone-level negative pressurization can should include “placing patients in neg- tals have obtained approval from local create what is effectively an isolation ative pressure rooms (airborne infection planning and development authorities to ward if adjacent zones are driven to pos- isolation rooms) or areas.” The Centers implement PR-HVAC at the room level. itive pressure. Controlled doors buffer for Disease Control and Prevention A closer look at the options available the elevator foyer and stairwells so the (CDC) advises “isolation of all persons to HVAC design engineers includes the pressurized zone is isolated effectively. with confirmed or probable pandemic following: The air handler can serve multiple zones influenza” in order to “delay the expo- Zone-level PR-HVAC. Using the or be dedicated to the pandemic zone. In nential growth in incident cases.” term “zone” rather than “floor” to refer either case, VAV airflow valves must be to HVAC control of an entire floor pre- used in sufficient numbers to enable all Pandemic-ready HVAC vents confusion with floor-type ventila- spaces of the zone to simultaneously pro- A pandemic-ready HVAC system (PR- tion systems that use under-floor distri- vide more exhaust airflow volume than HVAC) can take several forms, depending bution or displacement ventilation. supply, thereby creating the negative on whether the desired control is zone- The basis for zone-level and room-level space. Similarly, zones above and below level or room-level. designs assume the use of venturi airflow the pandemic zone must supply more air- Zone-level pressurization involves valves because they perform better than flow than exhaust so those spaces go posi- pressurizing floors above and below the air terminal units (ATUs) for maintaining tive. Positive adjacent zones ensure that pandemic floor, ensuring the pandemic the outlined pressure relationships under no infiltration of airborne pathogens pene- floor is negative. Room-level pressuriza- the varying conditions inherent in vari- trates the space from the pandemic zone. N O tion enables normal patient rooms (which able air volume (VAV) applications. During normal operation, the entire I T A are usually either neutral or slightly posi- Venturi valves don’t require flow sen- PR-HVAC zone can function as regular R O P

tive to the corridor) to become negative sors in the airstream to measure air flow patient rooms (neutral to the corridor), R O C

when needed as an airborne infection iso- rates. Flow sensors in ATUs are prone to with the ventilation operating for com- S lation (AII) room. The engineer designing clogging, especially in hospitals where fort conditions and energy efficiency. In L O R the system can use either approach or a bed linen particles get pulled into ex- the event of a pandemic incident, per- T N O combination to meet the unique needs haust units. When flow sensors clog, flow sonnel activate the PR-HVAC either C

X and layout of the building. rates are misreported to the building through a key-switch, panic button or I N E

While the Guidelines for Design and management system (BMS) and space via a command initiated at the BMS O H P Construction of Health Care Facilities pressurization can become compro- front-end. This initiates the following Y S require isolation rooms to be fixed as ei- mised. Furthermore, venturi valves deliv- sequence of operations: E T R ther positive or negative airflow spaces, er reliable airflow cubic feet per minute 1 / Control doors close in the pan- U O C guidelines for patient rooms specify no re- (CFM) rates under changing conditions demic zone and an audible alarm or an- S G

quirement for pressurization. And there is of duct static pressure, another common nouncement may sound. N I R nothing specific in current American Insti- problem in HVAC systems. For these rea- 2 / The pandemic zone increases to- E D N

tute of Architects or American Society of sons, venturi airflow valves are recom- tal exhaust CFM volume to 10 percent E Heating, Refrigerating and Air-Condition- mended for conditions where space pres- more than supply CFM. R Pandemic ready

3 / The pandemic zone control damp- room-level PR-HVAC is intended prima- valve and return air valve are ers change from air recirculation to 100 rily for new construction. The primary called a “tracking pair.” Thus, during percent outside exhaust. This means benefit of room-level control is that normal VAV operations, the two that ductwork for both recirculation and each room can be converted to negative valves track each other’s offset, always outside exhaust is installed downstream (or positive) pressure as required with- maintaining 50 CFM negative offset of the damper. High-efficiency particu- out disrupting services to other patients through increases or decreases in air- late air (HEPA) filtration on outside ex- on the floor. Depending on the number flow that may be used for occupied and haust should be installed to protect and frequency of arriving patients dur- unoccupied states. The exhaust valve is maintenance and other service person- ing a surge, hospital staff can decide if independently controlled by the BMS. nel from infectious agents at ventilation and when to dedicate the entire zone to When pandemic mode is required, the stack locations. pandemic operations. following sequence is initiated: 4 / Adjacent zones increase total supply There are two room-level pandemic se- 1 / The return air valve moves from CFM to 10 percent more than the exhaust. quences to consider. One uses constant tracking the supply valve to shutoff po- Most suitable in retrofit situations, ba- volume venturi valves with damper con- sition, disabling recirculation and seals sic zone-level PR-HVAC can be imple- trol and the other uses VAV venturi valves the return air duct from contamination. mented with minimal investment. with shutoff capability and no dampers. 2 / The BMS system simultaneously Perimeter control doors may need to be As with zone-level control, the room’s starts the exhaust fan corresponding to installed. More ductwork and dampers pandemic-mode sequence can be initiat- the exhaust air valve and controls it to would be needed to separate recircula- ed by a key-switch, panic button or a maintain adequate (0.3-inch water tion and outside exhaust. And addition- command initiated at the BMS. gauge or greater) duct static pressure. al BMS controllers may need to be pur- In a pandemic-mode sequence using 3 / The supply air and exhaust air chased and control sequences may need constant volume valves, the venturi valves switch to tracking mode, main- to be developed to control dampers in valves operate similar to an ATU but taining the 50 CFM negative offset and multiple zones. But, essentially, an en- with the benefits described earlier. The enabling 100 percent outside exhaust. tire pandemic-ready isolation ward can diagram on the upper left-hand side of 4 / In neighboring rooms, the ex- be created with these modifications. page 50 shows a pair of constant volume haust air valve remains shut off while However, there are some disadvan- valves in each patient room. The valves supply air and return air valves track for tages to zone-level PR-HVAC. One sus- are configured for fixed flow rates and normal energy-efficient operation. pected case of pandemic influenza paired so the installation delivers a pre- With an integrated VAV and shutoff ca- would mean the entire zone would need defined negative offset—in this case, pability in the device, pandemic mode can to convert procedurally and operational- 500 CFM supply and 450 CFM exhaust. also take place in the event of a power loss. ly to pandemic mode (assuming there During normal operations, Damper 2 Using spring-return actuators, the supply are no isolation rooms available). Staff is closed to disable outside exhaust and air and exhaust air valves can spring open would need to limit access to the zone, Damper 1 is open to provide energy-effi- to mechanical clamp (paired for 50 CFM activating their own preplanned pan- cient recirculation. HEPA filtration is not negative offset) and the return air actuator demic response procedures and remov- needed because recirculation will be dis- can spring closed. ing the zone from normal operational abled during pandemic-mode of opera- This type of VAV operation not only use for an undetermined period. tion. When pandemic-mode is required, serves the hospital in the event of a pan- There may be additional expenses as Damper 1 closes to disable recirculation demic, but also enables the most flexible well. Careful analysis should be and Damper 2 opens for 100 percent use of the space as needs evolve. Since performed regarding leakage in the outside exhaust. Because of the nature the rooms can be flipped to either building envelope and how this con- of venturi valve performance, the system negative or positive pressurization, the tributes to computing the volumetric off- will always deliver the predefined flow space can be used as acuity-adaptable set required to create the negative pres- rates and 50 CFM negative offset, keep- rooms or for minor surgeries. sure zone. Sealing fenestrations and ing the room negative. Other options. There are options measuring the results are expensive. In a pandemic-mode sequence using for pandemic response other than these Room-level PR-HVAC. The alterna- VAV shutoff valves, the venturi valves HVAC designs. For instance, with the tive to zone-level PR-HVAC is room-lev- with shutoff capability perform two right procedures in place and periodic el PR-HVAC. Room-level control pro- functions: They enable VAV but also mock-pandemic exercises, hospitals can vides more flexibility in the way the control the state of recirculation or full make plans to respond to an outbreak space can be used and creates more op- exhaust without requiring dampers using makeshift facilities for triage. portunities for energy savings during elsewhere in the ductwork. These can be erected rapidly using tents normal operations. The diagram on the upper right-hand with portable ventilation systems, rapid- Because the ability to run multistate side of page 50 shows three valves: a deployment containment spaces for pressurization in individual rooms is supply air valve, an exhaust air valve isolation wards and various other best planned at the start of a project, and a return air valve. The supply air systems that utilize inexpensive and Created from original published content in Health Facilities Management October 2008 Volume 21 Number 10 ©2008 copyright by Health Forum Inc. Published by Health Forum Inc. All rights reserved. For electronic use only–not for reprint purposes.

easy-to-store materials. intended pressurizations. run with a particle counter to assess These methods may result in Regardless of the design approach, it the efficacy of directional airflow and effective handling of patients if exe- is essential to ensure the PR-HVAC HEPA filters. cuted well, but there is a high risk of system functions as designed, so the fa- The threat of a pandemic is real. procedural error and equipment failure. cility is truly ready to contain a danger- Health facilities should take steps ous virus. This means the systems during renovation and new construc- Ensuring performance should be switched to pandemic mode tion to have systems ready to respond. PR-HVAC is a key component of modern annually for several days and monitored I hospital design. Room-level PR-HVAC at the BMS for proper pressurization. gives the facility the most flexibility to During operation it is important to veri- Michael Soper is a senior product use the space for a variety of services, fy at least 0.01-inch water gauge of differ- manager at Phoenix Controls energy efficiency and pandemic-prepar- ential pressure between the pandemic Corporation, an Acton, Massachu- edness. Zone-level PR-HVAC is a sensi- areas and reference spaces. This can be setts-based manufacturer of critical ble approach for retrofit application. measured using an airflow multimeter. airflow control systems for health And product choice for reliable HVAC A more exhaustive verification can be care facilities. He can be contacted at performance is critical to ensure the performed by augmenting the practice [email protected].

NORTHWEST COMMUNITY HOSPITAL PLANS PANDEMIC-READY PATIENT ROOMS orthwest Community Hospital, Arlington Heights, Ill., is building a new patient care addition that will offer the com- Nmunity state-of-the-art care in a modern structure designed for family-centered healing. The new building is de- . L

signed to harvest natural light and provide views of nature to aid in the healing process. Designed by OWP/P of Chica- L I

go, the project consists of 332,573 square feet of new and remodeled space, including a new entry and lobby, a 24-bed S T

critical care unit, labor and delivery rooms, post-surgical care rooms and a new parking garage. Slated for completion H G I in 2010, the nine-story tower will increase the hospital’s staffed bed count from 410 to 488, and include patient rooms E H

designed to accommodate a surge of potentially infectious patients. N O T

The mechanical systems on the fifth and ninth floors are designed to permit the hos- G N I pital to respond to a pandemic incident, should it ever occur in the community. Should L R A

pandemic influenza strike, the patient rooms on these floors can be used to isolate pa- , L A T

tients with the flu contagion, serving both the well-being of the patient and safety of I P

staff and the general public. S O H

These pandemic-ready patient rooms become isolation rooms on demand using a Y T I

building management system (BMS) command sequence that can be initiated by the N U

facility engineer. The BMS command causes the HVAC control system to change the M M O

balance of supply and exhaust air volumes to ensure that the direction of airflow is C

from clean to unclean areas in each patient room. Two cubic feet per minute (CFM) quantities and control se- S E

quences are specified: normal and emergency. Normal CFM quantities provide equal air volumes between supply W H T

and exhaust as well as central air recirculation to conserve energy. This enables neutral patient room-to-corridor R O N pressurization during normal day-to-day operations. When necessary, emergency CFM quantities provide more air Y S

volume to exhaust than supply, and full exhaust venting to the outdoors. This converts a normal patient room to a E T R

negative pressure bed or airborne infection isolation room. U O C

Using the right combination of variable air volume devices and controls, OWP/P was able to design a patient G N

space that provided an efficient and comfortable environment under normal operations, but that could respond I R E

immediately to the need for an isolation room in a public emergency. D N E R

Founded in 1985, Phoenix Controls Corporation is a recognized leader in the design and manufacture of precision airflow control systems for use in critical room environments. Theris® is Phoenix Controls’ family of variable air volume (VAV) and constant volume (CV) airflow control systems designed for healthcare facilities. Using Theris, health care facility owners can reduce maintenance costs, reduce the spread of airborne pathogens and conserve more energy. Learn more about how Theris can provide a pandemic-ready HVAC system at healthcare.phoenixcontrols.com.