Breathe easy with the right air purification & filtration systems
by Jeannie Akridge

Trane Commercial Systems

Some of the strictest standards for clean room conditions are found not only within the healthcare environment but also in industrial clean rooms throughout the world, in which contaminating particles could easily destroy millions of dollars worth of highly sensitive equipment. In the hospital environment, the costs of contaminants in the air could mean the life of a critically ill patient, or in the event of bioterrorism, the lives of many (see sidebar on pg. 26).

Clean room conditions in the hospital include isolation wards and the surgery suite. Both are mandated to specific pressure and air quality standards. The isolation ward is kept at a negative pressure, allowing air to flow into the room when the door is opened, thus protecting others in the hospital from the infected patient.

Conversely, the surgery suite should be kept at a positive pressure, meaning the air will flow outward when the door is opened, protecting the surgical patient from contaminants.

Humidity within any area of the hospital should be kept right around 50 to 55%, since bacteria thrive at both very high and very low levels of humidity. Temperature may vary slightly from surgery to surgery, but the humidity level should remain the same.

Another important consideration is the number of air exchanges per hour needed for specific areas of the hospital. For the operating room, CDC recommends fifteen air exchanges per hour. For isolation areas, the number of recommended air exchanges per hour is twelve.

In addition, the surgery suite should incorporate a laminar air flow. If the hospital does not have a laminar air flow system in the room, CDC recommends air supply to the room be brought in at the ceiling and exhausted near the floor.

For a list of references regarding hospital air quality conditions, see the chart on page 21.

For most hospitals a dedicated air supply unit will regulate these conditions within the surgery suite and even throughout the hospital. This article will explore some of the various components designed to improve air conditions throughout the hospital, in particular in clean room situations.

HVAC systems
At the core of any hospital’s air purification and filtration efforts is the HVAC system. While some older hospitals may have yet to enjoy such air conditioning luxury, it is certainly the standard for any modern hospital.

One company that makes the commercial components that make up an HVAC system, including chillers, air handling equipment and control systems, is Trane Commercial Systems. According to Steven Totty, director healthcare market for Trane, "It’s a control down to the micro level. It’s not just a control for the building, it’s controlling individual environments. A nurse, for example, could change the temperature setting in the surgery room from one operation to the next."

He notes that anyone who is installing or designing a hospital HVAC system, should be intimately familiar with the AIA Guidelines for Design and Construction of Hospitals and Healthcare Facilities. "It’s not just about the right components, but the application of the right components. A hospital could have a very efficient chiller, yet if the design and air handling of the system are not correct, then you’re not going to get the right temperature and humidity in the right place."

Totty points out that one of the most important things to consider regarding ventilation systems, is simply keeping the system clean. "It may be designed with the best and most expensive components, but if it’s not regularly cleaned, then efficiency is lost. And even more importantly, the energy usage will increase, because it’s harder for the motor to draw air across a dirty filter."

He explains that in addition to changing the filter in a timely manner, the duct work and drain pan must also be cleaned on a regular basis. "You need to take the time to clean as much of the inside of the system as you can physically reach."

Totty says that the Trane chillers, which account for about 50% of the chillers used in hospitals in the U.S. today, have been designed to be energy efficient. "The technology we use is based on the fact that the user is going to purchase the equipment based on total life cycle cost. We believe in the long run that if we bring to the user equipment that is really based on the most economical total life cycle cost analysis, then the hospital has the capital to invest back into revenue producing items such as an MRI."

He explains that Trane is on the constant lookout for new technology to make their chillers more efficient, air handlers smaller and more efficient, and controls more sensitive, and notes that their equipment is about 40% more efficient than it was twenty years ago.

Abatement HC400UV

Stand-alone units
Another option for keeping air within the hospital clean involves stand-alone ceiling mounted units such as those provided by Honeywell. Said Tim Kensok, director of indoor air quality products business for Honeywell, "The systems that we sell to the commercial market today are all stand-alone systems that don’t tie in directly to the central heating and air conditioning system of the building. They were designed to provide improved and incremental indoor air quality control for what would normally exist in the hospital environment."

IQAir Cleanroom

Scott Roberts, North American sales and marketing manager for commercial indoor air quality, Honeywell, said, "There have been a lot of reports that say that many nosocomial infections are airborne. It’s the one area that’s often not cleaned very well. They clean counters; the clean doorknobs; they wear rubber gloves. But the airborne transmission rate is usually considered a significant factor."

Kensok explains that the stand-alone units offer big advantages in a retrofit situation. "It’s usually much more cost effective to put a separate air quality system in than to have to make a lot of expensive changes to the heating and air conditioning side of the system." Honeywell’s permanently installed ceiling mounted air cleaners either flush-mount with a drop ceiling, or surface-mount on a solid ceiling, hanging down about a foot below the ceiling surface. With the systems, said Kensok, "We can manage air flows and manage pressures between different rooms and different parts of the room, and that can be a very effective tool in managing the flow of contaminants."

He describes three ways in which hospital administrators could improve the air quality in areas of the hospital that already have an HVAC system, for example in the emergency room. "One way is to increase the flow of outside air to flush out the space more often. While it would be an effective means to rid the space of bio-contaminants, the downside is you now have much higher energy costs to condition the air you’re bringing in from the outside.

"A second option would be to apply a higher level of filtration to the central air handling system. Again that may be effective in reducing the bio-contaminants, but the problem is those higher efficiency filters add resistance to air flow so now your energy costs for running the blower motor are increased, or you would have to replace your blower motor to get the air to move.

"The third option is a stand-alone unit, which is not at all disruptive to the central heating and cooling system, yet can provide the same benefits in terms of air cleaning as bringing in large amounts of outside air. Yet you don’t have the energy penalties associated with conditioning that air."

Abatement Technologies also offers ceiling mounted stand-alone units. David Shagott, president of Abatement, notes "the ceiling units are popular for situations where they don’t want a portable in the room of any size taking up space, and are especially popular for creating permanent isolation rooms."

He notes that for hospitals that do not have a horizontal laminar air flow in the operating room, the ceiling units can help provide the high to low air flow direction recommended by the CDC. "They can ensure that any of the air that is fed into the room first passes through 99.99 percent HEPA filters and also these units can increase the amount of air flowing into the room so they can help maintain positive pressure within the room." Shagott says that Abatement’s HEPA-CARE systems can also help hospitals meet the 15 air exchanges per hour necessary in a surgery setting.

Blueair

Portable units
An alternative to ceiling mounted units that offer additional flexibility for hospitals are portable air cleaning devices. Shagott says Abatement’s portable models offer hospitals the flexibility to set up patient isolation wherever they may need it. "They can move these portables from room to room and pretty quickly implement a negative or positive pressure environment in the room."

In addition, the portable units allow you to move the units closer to the source of contamination, whether that be an individual or an area of the room.

IQAir also makes portable air purification units. The company offers a HealthPro line as well as a Cleanroom series. Glory Dolphin, CIE, CAFS, chief executive officer, IQAir, explains that the Cleanroom series H13 model was used in 1998 during the first open heart surgery performed in South America.

Dolphin explains that another application for the portable devices has been with the wildfires in Los Angeles, where a lot of emergency rooms were inundated with people experiencing asthma and allergy problems. With the systems in the waiting room, hospitals were able to help purify the air enough to give walk-ins some instant relief.

Abatement HC400F

IQAir’s air cleaners are individually tested, so that each one has its own certificate of performance. The units are available with inflow attachments that allow the Cleanroom series to maintain positive or negative pressure.

Airsonett, a company from Sweden, with U.S. headquarters in Atlanta, GA, offers an even more specialized air cleaning system with its Airshower. The Airshower was designed to provide a highly concentrated "zone" of clean air directly to the breathing space of an individual. The units were originally designed for industrial clean room use in Europe. According to Dan Kristensson, president of Airsonett, the Airshower has the unique ability to create clean room conditions with very little mixture of the surrounding air into the clean air zone. The unit has been introduced in the United States initially marketed as a treatment device for those suffering with upper respiratory allergies and asthma. He remarks however, that there are a number of applications within a hospital environment, including post-operative care."

Airsonett Airshower

According to Kristensson, the Airshower is able to create clean room conditions of much less than 5,000 particles within the zone of the device, in about three minutes. The unit is also effective at cleaning the entire room.

A unique feature of the Airshower is the way in which it works. The unit has a built-in dual element that respectively heats and cools two separate flows of purified air one to two degrees relevant to ambient air. The cooled purified air is delivered about 20 inches above the individual’s head. Being slightly denser, the air descends slowly, replacing the contaminated air around the individual. The heated purified air rises toward the ceiling, then slowly descends, where it is eventually evacuated in the air intake of the unit at the floor level.

A future potential application for the Airshower could be to include medication or some other form of treatment, for example for asthma, in the air supply. "We could supply a higher level of oxygen or maybe some kind of medical treatment, but we have not done so yet, said Kristensson. "It’s still in the experimental stage."

Another company with Swedish origins is Blueair, with U.S. headquarters in Chicago. The company offers smaller capacity air purification devices that are rated by the FDA as a medical device. The Blueair devices are compact, quiet, Energy-Star rated, yet highly efficient, portable air cleaning devices. Its HEPA filter system has been tested to capture 99.97% of airborne particles at 0.1 micron. The company also offers hospitals a filter subscription service.

Camfil Farr Camsorb Filter

Filters
At the heart of many of these air purification devices is the filter itself. CDC recommends HEPA filtration within many areas of the hospital. Filters that are HEPA-rated are 99.97% efficient at removing particles sized at 0.3 microns or smaller. HEPA filters rate in the highest ASHRAE standards of MERV (Minimum Efficiency Reporting Values) testing. A newer and even more efficient filter is the ULPA (Ultra Low Penetrating Air).

While many of the products mentioned in this article employ HEPA filters, several companies incorporate additional methods of purifying the air.

IQAir’s HEPA filters are made of an antimicrobial material, which Dolphin claims will disable the DNA of any microorganism that gets captured in the filter. The company’s Cleanroom series has achieved EN-1822 certification which is, to date, the world’s most stringent HEPA filter test. The EN (European Norm) 1822 is a two part test, which identifies the particle size that penetrates the HEPA filter most easily. Dolphin explains that companies such as Intel are now requiring EN-1822 certification for their filtration products.

She also explains that the EN-1822 is also more stringent than the standard ASHRAE MERV test which is currently being used to rate filter efficiency.

"The minimum requirement for air filtration into operating rooms is 90% ASHRAE efficiency, and that’s a long way from HEPA. ASHRAE efficiency is measured in a test that’s looking at much larger particles," adds Shagott.

He notes, "Each and every HEPA filter that is put into our units has to provide a minimum overall efficiency of 99.99% when challenged with a 0.3 micron test aerosol. And that exceeds the requirements for HEPA filters used in hospitals."

Abatement also includes antimicrobial-treated filters in its products, along with gel-sealed pharmaceutical grade HEPA filters.

Camfil Farr is by far one of the world’s largest manufacturers of filters. The company offers a multitude of filters with a variety of efficiencies and energy saving measures, to fit virtually any HVAC system out there. The company offers a wealth of information on its Web site regarding filtration requirements established by the U.S. Department of Health and Human Services and ASHRAE, to name a few (www.camfilfarr.com).

In addition to efficiency, you’ll need to consider the filter’s capacity to hold contaminants.

"If you have a filter that does not have the capacity to hold as much of the contaminants and has to be changed three times as often, the labor involved in doing that is going to more than offset the cost of the higher-capacity filter," relates Totty.

Steril-Aire UVC

UVC devices
As an additional precautionary measure, CDC recommends the use of UV to supplement (but not replace) HEPA filtration and provide additional clean air change equivalents in situations where the need for additional measures is indicated by an Infection Control Risk Analysis (ICRA).

One company that supplies UVC devices specifically designed for that purpose is Steril-Aire. Roger Stamper, vice president sales and marketing, clarifies that his company has designed a unit that will work in cold moving air such as an HVAC system. "One of the problems with the old-school style UV products and even a number of them on the market today, is they have trouble operating in cold moving air; in other words, producing enough energy to kill the microorganisms."

The UVC devices are generally placed near the cooling coil of the HVAC system in an effort to reduce mold that tends to form due to the water that is generated around the cooling coils. This not only provides the advantage of minimizing contaminants, but also allows the system to function properly resulting in added efficiency and energy savings. Stamper also says the UVC lights will extend the life of the final HEPA filters by ensuring that they’re not loaded up with mold or other contaminants. In addition, it greatly reduces the amount of cleaning that’s necessary with the drain pan.

Steril-Aire UVC

Stamper advises that in order to get a higher kill rate for airborne microorganisms, you’ll need to increase the number of UVC lights. He explains that there has been significant testing on the ability of UVC devices to kill a wide variety of bacteria and viruses, including a University of Buffalo test that showed it was effective against SARS. He says the Research Triangle Institute is testing UVC products on the market, in a study funded in part by the EPA, in an effort to help ASHRAE determine a standard for rating the products’ effectiveness.

"It was never a question of whether UV kills microorganisms, but whether we could get it to function on airborne microorganisms. We now have data that proves that also. It’s simply a matter of dosage, which is time of exposure that an organism needs and the amount of energy that you can produce from a combination of tubes to destroy that microorganism in sometimes the millisecond that you have it exposed to it."

He adds, "We’re not going to replace any filters. What we’re going to do is enhance their ability to do some things and assist them in eliminating some problems that filters can’t."

He explains that while some viruses are small enough to pass through HEPA filters, the UVC lights will actually destroy the DNA or RNA of the virus.

While currently, the CDC is only recommending, and not mandating, the use of UVC devices, Stamper said the organization has done quite a bit of testing in the past few years, which he believes will lead to a stronger endorsement.

Steril-Aire UVC emitters are rated to maintain its kill rate over the entire life of the tube, which is generally around one year, or 9,000 hours. In fact, notes Stamper, Steril-Aire has twelve patents which allow them to verify that. The company also sells a device known as a radiometer which measures the UVC output of the tubes.

Other companies such as Honeywell and Abatement have incorporated UV into recent product introductions.

Shagott said, "In positive pressure environments our germicidal UV modules can be used to disinfect HVAC supply air before it is fed into the room. In negative pressure applications they can be used to disinfect air exhausted from the room."

IQAir ParticleScan

Monitoring systems
Even with reliable filtration systems and maintenance standards in place, it will still be necessary to monitor systems for a variety of conditions. An assortment of tools are available to help with this task.

Of course it will be important to measure pressures throughout the hospital. Under the current CDC recommendations, hospitals are required to check the pressure of patient isolation rooms daily. One company that sells electronic pressure monitors is Abatement. Says Shagott, "We have both a fixed unit that mounts to the wall and a portable unit that you can take from room to room. The fixed unit is compatible with the hospital’s automation system, or is available with a land module to provide 24/7 pressure monitoring."

A company called Setra Systems, Inc. provides low differential pressure sensors that are accurate enough to measure the minute pressure differentials throughout the hospital, and in particular the ope

Setra 267

rating room, with its ASHRAE-recommended 0.1 inches of water column pressure. Explains Terry Troyer, HVAC marketing manager for Setra, "Our pressure sensors, because of our unique capacitance technology, are accurate and sensitive enough to measure extremely low differential pressures. Not all suppliers can service this particular niche."

Steril-Aire radiometer

The pressure transducers are most often installed in the HVAC system as a continuous resident monitor and control, connected to the building’s automation system. The transducers can also be used to measure the cleanliness of filters by measuring the pressure difference between the supply and discharge sides of the filter. Setra supplies it systems to most of the large HVAC manufacturers, including Trane, Johnson Controls, Siemens and Honeywell.

Another way to monitor the cleanliness of air filters, other than the antiquated method of visual inspection, is by monitoring the air flow through the filter.

According to Ken Bloom of Precision Air Technologies, the company’s Filtrometer can help facilities determine the best time to change the air filter, resulting in energy savings, while keeping the HVAC system running in peak condition. The Filtrometer could even serve as a diagnostic tool for the entire HVAC system, says Bloom. The monitor, which can be connected to the hospital’s automation system, will also provide an alert if the wrong type of filter is installed.

To measure the cleanliness of the air, Abatement offers a laser particle counter that measures particles down to 0.1 micron. IQAir’s ParticleScan is another such device.

The use of these types of monitoring products will not only help keep hospitals in line with regulations and help maintain optimal patient conditions, but will also keep systems working in peak condition and energy efficiencies at their best.

Emergency management considerations

In addition to protecting the facility on a daily basis from normally existing microorganisms, air purification and filtration systems will play an important role in protecting those in the facility in the event of a bioterrorism event.For more details on preparing for a bioterrorism event, see the sidebar on page 26. HPN