Air/Room Sterilization is the Newest Way to Eliminate Contaminants

Indoor air in a healthcare environment is a veritable invisible cloud of particulate matter, microorganisms (including spores, viruses and bacteria) and volatile organic compounds (emitted by cleaning products and furniture) dust, lint from hospital linens and fabrics, surgical smoke, and even pollen and animal dander brought in on the clothes of staff, patients and visitors. Traces of chemicals, gases and fumes can also be present. Surfaces can become contaminated with fallen particulate matter that can then be picked up and transferred on the hands of healthcare workers.

One new way of battling these contaminants is air/room sterilization, with several technology options available currently:

• STERIS Corporation offers advanced room sterilization with the VaproSure Sterilizer, featuring Vaprox® Sterilant, when used as part of a room’s terminal cleaning program. The VaproSure Sterilizer is a low-temperature dry vapor designed to destroy a full spectrum of biological contaminants, including spores, bacteria, viruses and fungi, leaving no residue and no lingering odor.

• The PlasmairT2006 with HEPA-MD technology from AirInSpace is a Food and Drug Administration (FDA)-cleared mobile air decontamination unit which multi-year clinical study data suggests can contribute to reducing the incidence of airborne aspergillosis infection. The AirInSpace technology is designed to demonstrate up to 99.999 percent single-pass inactivation of airborne microorganisms.

• Xenex Technologies, Inc. offers two portable xenon pulse UV sterilization devices that produce brief pulse of intense UV light that penetrates the cell walls of viruses, bacterium, fungi and mold to fuse the strands of DNA (creating thymine dimers), resulting in cell death. The devices are portable, can be operated by one person with minimal training and can sterilize the air and visible surfaces in a room in minutes. These devices are able to kill bacterial spores at a distance of 2 meters from the lamp in 8 minutes without the use of any chemicals.

• Advanced Vapor Technologies’ TANCS steam vapor disinfection system is designed to disinfect surfaces colonized by the Acinetobacter baumannii, which can cause a variety of diseases, ranging from pneumonia to serious blood or wound infections.

Technologically advanced systems such as these can pick up where traditional environmental cleaning leaves off.

Nick Jacobs, product manager for Infection Prevention Technologies for STERIS, notes, “Recent studies suggest that environmental contamination is a likely source of infection transmission. Despite the best efforts of the environmental services department, cleaners and chemicals are limited in their effectiveness against the most virulent organisms. By adding the VaproSure™ Sterilizer to their arsenal, hospitals can now sterilize all the exposed surfaces in rooms where contamination can put patients most at risk.”

In 2006, after 15 years of documented applications, STERIS obtained approval to expand the use of Vaprox Sterilant, the liquid sterilant used in combination with the VaproSure Sterilizer, for the sterilization of dry, pre-cleaned, porous and nonporous exposed surfaces within hospital rooms and emergency vehicles. The VaproSure Sterilizer sterilizes in four microprocessor-controlled phases, providing a dry sterilization process that produces only water vapor and oxygen as by-products.

Airborne pathogens can be deadly for immunocompromised individuals, so air/room sterilization systems play an important preventive role. At this year’s annual meeting of the Association for Professionals in Infection Control and Epidemiology (APIC), Ludwig Aho-Glélé, MD, an epidemiologist and director of infection control at Dijon University Hospital, presented data during the AirInSpace-sponsored symposium, “Strategies for Airborne Infection Control Under Challenging Environments and Patient Conditions.” Presenting with Aho-Glélé was Michael S. Phillips, MD, an epidemiologist at New York University Medical Center, and Wayne R. Thomann, PhD, director of occupational and environmental safety at Duke University Health System. “Invasive aspergillosis is a potentially deadly infection for immune-suppressed hospital patients,” says Aho-Glélé. “The Centers for Disease Control and Prevention (CDC) reports a mortality rate of 95 percent in immune-suppressed patients who are recipients of allogeneic bone marrow transplants and patients who have aplastic anemia. These patients need a highly protective environment.”

In July, Texas-based Antimicrobial Test Laboratories conducted two studies, each utilizing five individual test surfaces, to evaluate the capability of the TANCS system. “For each experiment, greater than 10 million viable A. baumannii in a 5 percent artificial soil suspension were spread over porous clay surfaces,” explains Benjamin Tanner, PhD, president of Antimicrobial Test Laboratories. “At least 2 million viable A. baumannii cells were present on each test surface after the inoculum was dried to create a film. The surfaces were then treated briefly with the saturated steam device, for periods of 0.5, 1, 2 and 5 seconds. Immediately after treatment, test surfaces were transferred to a broth suspension for cooling and microbial enumeration by duplicate plating. Elution broth tubes were also incubated to enhance the detection limit or sensitivity for the study.”

The experiment demonstrated a rapid reduction in A. baumannii levels with increasing treatment time, Tanner said. The destruction of pathogens on the surfaces demonstrated “roughly log-linear kinetics,” with total disinfection of A. baumannii on the surface occurring within 5 seconds in both trials. Extraordinarily brief treatments of the surface also produced substantial reductions in the pathogen load; more than 97.5 percent of the bacteria were killed within the first 2 seconds of treatment.

TANCS® steam vapor systems offer a simple water-only cleaning and disinfection process. Heat, not pressure, does the deep cleaning and disinfecting. Contained, sustained heat breaks the bond between contaminants and a surface. “The saturated steam device tested here reduced levels of A. baumannii on surfaces quickly and dramatically,” Tanner says. “Microbial reductions in ‘real-life’ usage of the device may be greater than indicated by these studies, because they were conservative in that the surface was highly porous and was cooled immediately after treatment. The similarities in performance of the device between trials suggest that it is a reliable and consistent means to disinfect a surface contaminated with A. baumannii.”

Air/Room Sterilization Q&A


ICT posed a number of questions exploring this new concept to Mark Stibich, PhD, of Xenex Technologies and Nick Jacobs of STERIS Corp.


ICT: What is the most significant misperception clinicians have about the germicidal aspects of air and/or room sterilization and how can these misperceptions be corrected?


Stibich: The most significant misperception held about the role of air contamination in infection is that fomites play little or no role in respiratory infection. Boone and Gerba (2007) state that there is growing evidence that contaminated fomites play a key role in the spread of infection. There are three ways respiratory viruses are spread: direct person-to-person contact, the airborne route and via contaminated surfaces (fomites). For example, when a person sneezes there is some risk of infection via the airborne route; however, the infectious particles in that sneeze cover nearly every surface in a room. When a blanket is shaken, those particles become airborne again. Additionally, infectious particles are easily transferred from object to hand and pose a risk for infection again. An effective system to reduce infection must address all three of these routes through barrier protection, hand hygiene, air decontamination and (most often overlooked) surface decontamination. Another misconception is that air sterilization requires the use of caustic or dangerous gases or “dry mists” that require the room to be completely sealed. Using energy alone, pulse xenon ultraviolet (UV) light can effectively decontaminate the air in a room.


Jacobs: The most common misperception about the VaproSure™ Sterilizer is that it’s just another fogging system. The VaproSure Sterilizer produces a dry sterilant vapor, not a fog or mist.  As a result, there's more uniform coverage throughout the room and significantly less risk of material compatibility issues. Customers generally understand the difference, but it takes a little bit of education.


ICT: What do you believe is the most important scientific evidence behind air/room sterilization technology?


Stibich: UV light has been used for decontamination in laboratory and other settings for decades. The pulse xenon UV sterilization system used by Xenex Technologies has been field tested in international settings since 2005, including in a World Bank/Russian Ministry of Health joint TB control project. Our own claims are based on studies by the Russian National Academy of Sciences that we are currently validating in U.S. laboratories.


Jacobs: The most significant evidence supporting room sterilization is the Environmental Protection Agency (EPA) registration for our product (Reg. No. 58779-4). EPA rigorously tested the system and challenged it using the most difficult-to-kill spore for this technology, Geobacillus stearothermophilus. The outcome of this testing process was the registration of Vaprox® sterilant as a broad spectrum sterilant (not just a disinfectant) when it’s used with the VaproSure Sterilizer.


ICT: What do you believe are the most critical applications of this kind of technology in the healthcare environment, and how can it reduce healthcare-acquired infections?


Stibich: There are two types of critical applications for portable pulse xenon UV disinfection: protecting the immune-compromised and emergency response. For the immune-compromised (burn victims, chemotherapy patients, ICU patients, etc.) it is critical that the healthcare environment not pose a risk to their health through effective air and surface sterilization. Air and surfaces should be reliably sterilized (without the use of toxic chemicals) on a routine basis in contact precautions rooms, following the terminal cleaning of all patient rooms and routine use in other areas (such as break rooms, public spaces, etc.). Bundled with hand hygiene, equipment sterilization and other practices, pulse xenon UV sterilization could significantly impact the infection rates in healthcare settings. In emergency settings, pulse xenon UV can be used to efficiently decontaminate enclosed areas without increasing the risk to emergency response workers.


Jacobs: One important use for room sterilization technology today is to sterilize mobile equipment, such as stretchers, IV poles and blood pressure cuffs, which travel from room to room and are typically handled by numerous people between cleanings. Multiple studies have demonstrated that portable equipment can serve as a potential source of infection transmission either by direct contact or by contamination of a healthcare worker's hands. Despite the best efforts of environmental services departments, cleaners and chemicals are limited in their effectiveness against the most virulent organisms. With the VaproSure Sterilizer, hospitals can ensure that this one potential source of transmission is eliminated altogether.



Boone S.A and Gerba CP. Significance of fomites in the spread of respiratory and enteric viral disease. Applied and Environmental Microbiology, 73(6),1687-96. 2007.