Introduction to Infrastructure Design for Reduced Patient Readmissions| April 23, 2018
Don’t Just Stop It, Eliminate It
High-efficiency filtration has always been a part of clinical and cleanroom airflow design. The benefits, which can include reduced patient infection rates, improved manufacturing defect rates, more consistent research environments, and many others, are obvious. Controlling airborne contaminant levels is a non-negotiable element in the engineering of a regulated environment.
However, in recent years a number of newer technologies have arrived which promise to go a step further. Where a traditional, even high-efficiency, filter will only passively catch particles of a certain size, there are active systems that, in particular, work to address contaminants at the molecular level.
Ultra-violet (UV) Lighting
The use of ultra-violet (UV) lighting in air treatment is a widely understood and available technology, which has been in use for many years. Specifically, UV-C (characterized as “short-wavelength”, around 260-270 nm) radiation is introduced into the airstream to neutralize the effects of airborne contaminants like bacteria and viruses. This UV-C light will actually affect the DNA of a microorganism, which might also include molds or other infectious agents, rendering it unable to reproduce.
Typically, a UV-C light source, either a mercury- or xenon-based lamp or a UV LED, will be installed in an air handler airstream. UV radiation, being harmful to human skin, must be contained within the equipment and operated automatically. Further, because UV is effective based on line-of-sight to the airstream, placement of the light source is key to achieving desired results. Often, multiple sources must be used as a system to cover the entire cross-section of the air handler tunnel.
UV-C radiation can be effective to the point of near sterilization. Provided the dose to the microorganism, taking into account the UV intensity and exposure time, is heavy enough, radiation at the wavelengths mentioned above will result in disinfection rates over 99%.
A new technology currently being researched and developed is the use of far-UV-C (210-220 nm) radiation. Studies are in progress, but testing has shown that this type of light will be approximately 95% effective in mitigation of airborne pathogens, while also being safe for human exposure.
This method of disinfection could be deployed in several ways, notably as a fixture, or system of fixtures to accommodate line-of-sight, no differently than any other ceiling light fixture. Appropriate locations include public areas such as malls, airports and, important to the clinical engineering community, emergency department (ED) waiting rooms.
Even while performing less effectively than traditional UV-C methods, use of far-UV-C in such a way would be a more cost-effective option which would also be more flexible and less complicated. Perhaps after the testing and data collection period, ED air change rate requirements might be able to be lowered when far-UV-C is used.
Traditional filtration is a very mature field, and the available and widely-used media are very good at what they do. Basically, the filter gets in the way of solid particles suspended in the airflow and blocks them from continuing on downstream.
When the contaminant is in the gaseous phase, though, it will pass through the filter with the rest of the air. This includes everything from simply a distracting but harmless odor to diesel engine exhaust emissions and volatile organic compound (VOC) off gassing. Because of the typically organic nature of these irritants, a filter made with activated carbon may be used to mitigate the issue.
Activated carbon is a processed carbon material integrated in the traditional filter media. It has a massive surface area which promotes high exposure for these organic compounds to form a bond at the molecular level and change the chemistry of the contaminant.
Similar to a traditional media in that it relies on contact with the gaseous pathogen to work, the efficiency of an activated carbon filter will be relative to the density of the material. Typical practice is to install downstream of traditional filtration to protect the costlier carbon media from getting too dirty too quickly.
As we all know, in the facilities engineering and management field, the building systems have to work. If the purpose of the facility is keeping people healthy, specialized manufacturing, or high-level research work, a well-thought out filtration and disinfection scheme is needed. We at F&T are the experts and we’re here to help develop a plan which will cost-effectively and energy-efficiently promote the good health of your operations.
Keep your eyes open for our upcoming guide on Infrastructure Design for Reduced Patient Readmissions!
 Far-UVC Light: A New Tool to Control the Spread of Airborne-Mediated Microbial Diseases. David Welch et. al., Scientific Reports, Article number 2752, Nature.com, Feb 9, 2018.