Air ways

Air control, filtration and ventilation technologies can improve the health care environment and help facility managers meet the special performance considerations inherent in hospitals.

Hospital facility managers must deal with rigorous performance requirements when it comes to improving indoor air quality (IAQ). What's more, these design considerations are regulated by organizations that write codes and standards for hospital construction.

The primary IAQ standard is the American National Standards Institute/American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)/American Society for Healthcare Engineering Standard 170 Ventilation of Health Care Facilities, which has been incorporated into the Facility Guidelines Institute's Guidelines for Design and Construction of Health Care Facilities.

The document lists more than 70 types of hospital spaces and a number of parameters, including pressure relationships to adjacent areas, minimum air changes per hour, minimum outdoor air, temperature and humidity. Thus, facility managers need to be familiar with the standard and the interrelationship of these parameters.

"Because hospitals are one of the few commercial building types that have such stringent requirements, the definition of how to achieve proper IAQ is pretty straightforward," says Justin Dascoli, health care market manager, Phoenix Controls, Acton, Mass. "The hard part is having the right technology and maintenance practices to make sure those requirements are continually upheld over the life of the building."

Available tools

Richard D. Hermans, P.E., HFDP, director of training and advanced applications, McQuay International, Minneapolis, and chair of the committee that developed Standard 170, says technology is available to provide better control of temperature and humidity, as well as handle infection control and cross contamination in hospitals.

"The tools are numerous and include accurate sensing of the condition of the environment, the capacity to condition the air regardless of the weather or the intensity of the thermal energies expended in the clinical process, and the continuous monitoring of that conditioning equipment for effective, efficient performance," Hermans explains.

Hermans says managers must consider four factors in their quest to improve indoor air quality: "Number one is filtration. Pathogenic organisms are particles, and filters control particles. Number two is air quantity. Standards are written to require certain volumes of both outside and recirculated air to reduce the risk of pathogens infecting patients. The third is remote monitoring and control of equipment. Airflows must be monitored constantly for performance. Room pressure relationships must be communicated both to facility managers and to clinical staff. The fourth is airflow patterns. How air moves within clinical spaces is just as important as how clean it is for the purposes of infection control."

Heating, ventilation and air conditioning (HVAC) systems play the largest role in maintaining IAQ and optimizing the health care environment, experts agree. These systems improve and control IAQ by heating or cooling the air, providing humidification or dehumidification as needed, and lowering the number of certain airborne contaminants, according to Dan Pollock, systems specialist for Trane, a brand of Ingersoll Rand, Davidson, N.C. "HVAC systems also bring in outside air, which helps control gaseous indoor emissions and volatile organic compounds (VOCs) from furnishings and construction materials as well as bioeffluents emitted by occupants."

Clean operations

To make sure an HVAC system is, in fact, maintaining a high-quality IAQ environment, facility managers need to keep close tabs on the following factors, according to Kevin Schreiber, global director of health care products, Huntair Inc., Tualatin, Ore.

Maintenance practices. Properly maintained equipment not only can improve IAQ, it also can maintain peak efficiency. Changing filters is just one requirement.

Control systems. Does the current control system address current operating requirements?

Air handlers. Are they capable of meeting current capacity requirements? How do they stack up in terms of operating efficiency with modern equipment?

Operating rooms. Are they designed to meet current airflow requirements? What type of filtration is used before that airflow enters the operating room and how is that air controlled to protect the patient?

Measures of success

"A very basic requirement is to measure IAQ," says Steve Tom, director of technical information, Automated Logic Corp., Kennesaw, Ga. "You can't manage what you don't measure. There are sophisticated monitoring systems on the market today that integrate well with building automation systems. These may be most appropriate for critical areas like operating rooms and intensive care units." Tom says reliable combination sensors for temperature, humidity and VOCs also are available at prices that allow them to be used in every room.

Additionally, low-cost carbon dioxide (CO2) sensors can be used to ensure areas are being properly ventilated. While these sensors provide raw data, the data alone do not ensure good IAQ. "It's important to process that data into actionable information," Tom explains. "A temperature reading by itself provides little information. Operating rooms, recovery rooms and patient rooms typically need to be at different temperatures. How does the temperature of a room compare with the desired temperature for that room? Is the humidity within reasonable limits? What about the VOC or CO2 levels?"

Tom recommends combining these readings into an environmental index, a rating from 0 to 100 percent that indicates how well the HVAC system is doing at maintaining these values within desired levels. If everything is within tolerance, the rating is 100 percent. If any one of these measured values is not within its ideal range, the rating drops. "By assigning a numerical rating, hospital facility managers easily can compare areas or track how well conditions are being met over time. They can compare the IAQ rating before and after changes have been made to their HVAC system," he adds.

Dale Kondik, P.E., CEM, health care development leader, Johnson Controls, Milwaukee, says hospital facility managers should conduct IAQ audits on a regular basis.

"As hospitals expand and renovate, interior space frequently is reprogrammed," he explains. "Hospitals can be overfiltering space that has a less stringent use, resulting in unnecessary fan energy needed to compensate for the higher level of filtration. An audit of air handlers, filtration level and areas served can help ensure proper filtration at minimum energy input. Verifying volumetric air changes during the same audit can result in further energy savings by reducing the amount of air being distributed and reheated."

Changing technology

New technology is available to improve air filtration, air quantity, airflow patterns, and remote monitoring and control of equipment. Displacement ventilation is one.

Based on a relatively new technology, displacement ventilation systems introduce cool air at low velocity, improving ventilation effectiveness within the occupant zone, according to a Department of Energy (DOE) report on hospital HVAC systems and energy management (http://apps1.eere.energy.gov/buildings/publications/pdfs/alliances/hea_hvac_fs.pdf). As a room becomes warmer through use, the air and its contaminants rise, generally resulting in better air quality than exists in traditionally ventilated areas. Additional benefits of displacement ventilation include:

• Saving energy by reducing ventilation air changes per hour (ACH);

• Decreasing ducts, saving floor-to-floor height;

• Reducing chiller lift and improving efficiency because supply air is 65 rather than 55 degrees Fahrenheit.

According to the DOE report, recent findings of the Healthcare Ventilation Research Collaborative (based on actual measurements) indicate that displacement ventilation with 4 ACH provides the same or better air quality for patient rooms than mixing ventilation at 6 ACH.

Liquid desiccant technology is another energy-efficient solution that is effective at dehumidification and air filtration, says Hannah Granade, president of Advantix Systems, North Miami Beach, Fla.

"Liquid desiccant systems use a nontoxic saltwater solution that works as a natural disinfectant. The desiccant solution scrubs air clean, removing 80 percent of particulates, 91 percent of airborne microorganisms and unpleasant odors in a single pass," she says. "Unlike conventional systems, these units do not use air filters that have to be cleaned and replaced."

Charlie Gans, vice president of global sales, Strobic Air Corp., Harleysville, Pa., says the largest IAQ technology change has been the evolution of inverters, sensors and controls. "The efficiency and reliability of inverters has im­proved greatly over the years," he notes. "[Variable-frequency drives] allow users to reduce the energy consumption of such mechanical equipment as pumps and fans. Their ability to interact with sensors and controls has increased exponentially over the years. Sensors and controls have followed the same path."

Innovative use of existing technology can improve IAQ as well. Dascoli of Phoenix Controls sees increased use of variable air volume venturi valves in health care facilities.

"There is a logical place for this technology in hospitals," he says. "Not only is the importance of having reliable airflow control important to maintain things like pressure relationships, but it also affects temperature, which impacts patient comfort."

Experts agree that IAQ equipment needs to move energy around a health care facility as efficiently as possible. For example, moving thermal energy with a fluid such as water or refrigerant is more efficient than moving the same amount of thermal energy with air, and fluids use less physical space to do so.

"A building system has to be able to react to quick-changing cooling and heating loads within a facility while expending the least amount of energy to achieve the level of comfort required," explains J. Patrick Banse, senior mechanical engineer with consulting firm Smith Seckman Reid Inc., Houston. Having sensors with control feedback and constant monitoring along with reset and setback control points allow this, he adds.

"Hospitals often use ventilation air as a 'dilution technique' for indoor air quality. The belief is that frequent air-change circulation will provide for a better environment," says Chuck McKinney, vice president of marketing for Aircuity Inc., Newton, Mass. "Unfortunately, indiscriminately maintaining high rates of air circulation wastes energy when the HVAC system is replacing clean air with clean air."

McKinney says new systems are available that both monitor and control ventilation rates to optimize energy use and IAQ. When the monitored areas of a hospital are "clean," the ventilation rates may be reduced to save energy (e.g., in a waiting area that is empty late in the day), he explains. If those areas experience a rise in contaminants, ventilation rates can be increased, providing a more comfortable environment.

Does the quality of ventilation affect infection control? Although few formal studies have been completed and results made public, experts point to ASHRAE's position as a guideline; it states:

• Many infectious diseases are transmitted through inhalation of droplet nuclei.

• Droplet nuclei can be disseminated through building ventilation systems.

• Airborne infectious disease transmission can be reduced by using dilution ventilation, in-room flow regimens, room-pressure differentials, personalized and source capture ventilation and air cleaning.

"ASHRAE has recommended further research on the development of more engineering control strategies to reduce infectious disease transmission," says Pollock of Trane. "In the interim, design professionals can benefit from understanding and considering the control measures available today, which include ultraviolet germicidal irradiation, dilution ventilation and space pressure differential."

Continuing evolution

As Standard 170 continues to evolve, health care facility managers need to stay abreast of the latest changes.

"Those of us who wrote ANSI/ASHRAE/ASHE Standard 170 Ventilation of Health Care Facilities have brought our life ex­periences to the establishment of practical and effective designs for hospital ventilation," concludes Hermans, who helped bring the standard to reality. "We continue to modify the standard to address new technologies and modern design practices so that the industry constantly improves."

Neal Lorenzi is a freelance writer based in Mundelein, Ill.