The heating, ventilation and air conditioning (HVAC) industry is faced with two substantial and growing challenges related to controlling and maintaining indoor air quality (IAQ). First, there is the need for continuous healthy air in all types of buildings, including government facilities, commercial offices, hospitals and residences. Air quality has been degraded in many buildings because of the conflict between maintaining strict indoor climate control and satisfying energy efficiency needs. Unhealthy indoor air leads to increased disease transmission, which in mild cases leads to absenteeism and lower productivity, and in severe cases leads to substantial and prolonged illnesses. The second, less prevalent, yet more ominous challenge is to provide inherent protection of a building from a purposeful biological agent attack.
A building's HVAC system is like a circulatory system that delivers the air for building occupants to breathe. In the process, it conditions the air (adjusts the temperature and humidity level) and cleans the air (removes airborne chemicals and particles, including microorganisms) to meet the needs of the space. The current state-of-the-art in air cleaning is filtration. While filtration alone when done properly is effective, it has serious drawbacks related to installation and maintenance practices. For a filter to perform properly it must be sealed against the duct face; otherwise, air will bypass the filter, carrying with it any present contamination. Filters in HVAC systems are changed repeatedly, as often as once a month, and as such are prone at some point, to misalignment. It has been estimated that between five and ten percent of all "filtered" air is actually bypassed.
When microorganisms, particularly molds, accumulate on filters or anywhere in an HVAC system, they can multiply and re-release into the ductwork and the conditioned space. The phenomenon of filter grow through is well documented in literature, and causes progressive introduction of new microorganisms into what should be clean air.
In attack scenarios, large doses of lethal microorganisms are introduced to a building's HVAC system, and even with excess levels of filtration, many will get through. Also, the high concentrations of attack agents that are caught render filters highly lethal, and apt to re-introduce organisms with even slight movement. Removing contaminated filters then becomes a highly specialized and dangerous task.
At present there are no cost effective technologies for killing airborne microorganisms to levels necessary for preventing continued growth, for removing the threat of bio-attack, or for destroying airborne VOCs. Because microorganisms reproduce so aggressively, they must be eliminated nearly to the last cell. Current techniques for in-duct killing do not approach these levels.
Removal of unwanted chemicals from a buildings air stream, such as volatile organic compounds (VOCs) and toxic industrial chemicals (TICs), can be done with filtration in the same manner as for particulates. However, gas filters (typically activated carbon) have limited holding capacity and may require frequent changing and high maintenance costs. A system for regenerating the gas filter using OAUGDP® can cause a substantial reduction of maintenance on carbon gas filters.
AGT's Solution - The Enhanced Plasma Sterilized Air Filtration and Purification System
AGT has developed and patented a system for capturing and killing all airborne microorganisms and airborne chemicals. The Enhanced Plasma Sterilized (EPS) Air Filtration and Purification System uses highly reactive chemical species (RCS) generated in a duct-borne plasma reactor to react with and kill microorganisms and destroy airborne chemicals that pass through an HVAC system. It is based on AGT's unique One Atmosphere Uniform Glow Discharge Plasma (OAUGDP®) technology. The EPS System was a recipient of R&D Magazine's 2002 R&D 100 Award as one of the most innovative new technologies of 2002.
Figure 1. Illustration of the EPS System
The EPS System is a simple modular design that is scalable and easily retrofitted into existing HVAC systems. In Figure 2, the ducted version of the EPS System is illustrated. It is capable of killing or neutralizing all varieties of airborne microorganisms: mold and fungal spores, bacteria, viruses, and bacterial endospores which are the dormant form of disease agents like Bacillus anthracis (anthrax). Additionally, the system can destroy captured VOCs and extend the usable life of gas filtration components. Depending on the needs of a particular building, the EPS can be operated periodically, e.g. for daily use on filter banks, or continuously for emergency or higher protection needs. It can also operate on demand, perhaps prior to filter changing, or as a response to a detector system for threat agents. Flexibility and scalability, like the high degree of killing, are inherent attributes of the EPS System which make it easy to retrofit, as well as easy to incorporate into new construction.
Figure 2. Ducted Version of the EPS System
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