# Aerobiological engineering > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Aerobiological_engineering > Markdown URL: https://mediated.wiki/source/Aerobiological_engineering.md > Source: https://en.wikipedia.org/wiki/Aerobiological_engineering > Source revision: 1318174084 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{more citations needed|date=April 2019}} '''Aerobiological engineering''' is the science of designing buildings and systems to control airborne [pathogens](/source/pathogens) and [allergens](/source/allergens) in indoor environments. The most-common environments include commercial buildings, residences and hospitals. This field of study is important because controlled indoor climates generally tend to favor the survival and transmission of [contagious](/source/Contagious_disease) human pathogens as well as certain kinds of [fungi](/source/fungi) and [bacteria](/source/bacteria). ==Aerobiological engineering in healthcare facilities== Since [healthcare](/source/Health_care) facilities can house a number of different types of [patient](/source/patient)s who potentially have weakened [immune system](/source/immune_system)s, aerobiological engineering is of significant importance to engineers of [hospital](/source/hospital)s. The aerobiology that concerns designers of hospitals includes [viruses](/source/viruses), [bacteria](/source/bacteria), [fungi](/source/fungi), and other [microbiological](/source/Microbiology) products such as [endotoxin](/source/endotoxin)s, [mycotoxin](/source/mycotoxin)s, and [microbial volatile organic compounds](/source/Indoor_air_quality) (MVOC's). Bacteria and viruses, because of their small size, readily become airborne as bacterial [aerosol](/source/aerosol)s . Even large-sized droplets can remain suspended in the air for long periods if upward velocity of air in closed spaces exceed particle's downward velocity as dictated by their negligible mass.{{Cite journal |last1=Cole |first1=Eugene C. |last2=Cook |first2=Carl E. |date=1998 |title=Characterization of infectious aerosols in health care facilities: An aid to effective engineering controls and preventive strategies |journal=[American Journal of Infection Control](/source/American_Journal_of_Infection_Control) |volume=26 |issue=4 |pages=453–464 |doi=10.1016/S0196-6553(98)70046-X |issn=0196-6553 |pmc=7132666 |pmid=9721404}} Because of this, adequate precautions and mitigation techniques need to be taken with [indoor air quality](/source/indoor_air_quality) in hospitals dealing with [infectious disease](/source/infectious_disease)s. ===Ventilation systems=== At a minimum, [ventilation](/source/Ventilation_(architecture)) systems provide dilution and removal of airborne contaminants, which in general leads to improved indoor air quality and happier occupants. If filters are checked and replaced as needed, they can form an integral component of an immune building system designed to prevent the spread of diseases by airborne routes. They can also be used for pressurization of areas within buildings to provide [contamination](/source/contamination) control. ===Biocontamination in ventilation systems=== Ventilation systems can contribute to the microbial loading of indoor environment by drawing in [microbe](/source/microbe)s from outdoor air and by creating conditions for growth. When microbes land on a wet filter that has been collecting dust, they have the perfect medium on which to grow, and if they grow through the filter they have the potential to be aerosolized and carried throughout the building via the [HVAC control system](/source/HVAC_control_system). ===Dilution rates=== Bacteria in hospitals can be aerosolized when sick patients cough and sneeze and because of the large number of germs produced it is necessary that the number of air changes per hour (ACH) remain high in treatment and [operating room](/source/operating_room)s. The [American Society of Heating, Refrigerating and Air-Conditioning Engineers](/source/American_Society_of_Heating%2C_Refrigerating_and_Air-Conditioning_Engineers) typically recommends 12-25 ACH in treatment and [operating rooms](/source/Surgery) and 4-6 ACH in [intensive-care](/source/Intensive-care_medicine) rooms. For rooms containing [tuberculosis](/source/tuberculosis) patients, the [Centers for Disease Control and Prevention](/source/Centers_for_Disease_Control_and_Prevention) recommends an ACH of 6 to 12, with exhaust air being sent through high-efficiency-particulate-air ([HEPA](/source/HEPA)) filters before being sent outside. ===Pressurized isolation rooms=== In order to keep patients safe, hospitals use a range of technologies to combat airborne pathogens. Isolation rooms can be designed to feature positive or negative air-pressure flows. Positive-pressure rooms are used when there are patients who are extremely susceptible to disease, such as [HIV](/source/HIV) patients. For these patients, it is paramount to prevent the ingress of any microorganisms, including common fungi and bacteria that may be harmless to healthy people. These systems filter the air before delivery with a HEPA filter and then pump it into the isolation room at high pressure, which forces air from the isolation room out into the hallway. In a [negative-pressure system](/source/Negative_room_pressure), the focus is on keeping infectious diseases isolated by controlling the airflow and directing harmful aerosols away from health care workers and other occupied areas. Negative pressure isolation rooms keep contaminants and pathogens from reaching external areas. The most common application of these rooms in the health industry today is for isolating tuberculosis patients. To do this, the air is exhausted from the room at a rate greater than that at which it is being delivered. This makes it difficult for airborne disease to go from a contaminated area to a hospital hallway, because air is constantly being drawn into the room rather than escaping from it. ===Air sterilization processes=== The normal means for filtration in healthcare facilities is low-efficiency air filters outside the air-handling unit followed by the HEPA (High Efficiency Particulate Air) filters placed after the air-handling unit. To be HEPA-certified, filters must remove particles of 0.3 μm diameter, with at least a 99.97-percent efficiency. Air burners sterilize air that is leaving contaminated isolation rooms by heating it to {{convert|300|C|F|0}} for six seconds. [Ultraviolet germicidal irradiation](/source/Ultraviolet_germicidal_irradiation) (UVGI) is another technique for special-purpose air sterilization. It is defined as electromagnetic radiation in the range of about 200 to 320 nm, that is used to destroy microorganisms. When HEPA filters are used in conjunction with UV sterilization tools, the results can be extremely effective. The filter will remove the bigger, hardier spores, and all that is left are the smaller microbes which are killed more efficiently by the high-intensity UV treatment. ==See also== * [Human habitat](/source/%3ACategory%3AHuman_habitats) * [Human outpost](/source/Human_outpost) (artificially created controlled human habitat) * [Legionnaires' disease](/source/Legionnaires'_disease) * [Aerobiology](/source/Aerobiology) ==References== {{reflist}} * C.S. Cox ''The Aerobiological Pathway of Microorganisms''. Chichester G.B.: John Wiley & Sons 27, p. 118-119. * Godish, Thad. ''Indoor Environmental Quality''. Boca Raton, FL, USA: Lewis Publishers, 2001. p. 190. * Kowalski, Wladyslaw Jan. ''Aerobiological Engineering Handbook''. Blacklick, OH, USA: McGraw-Hill Professional Publishing, 2005. p. 6, 185, 231, 260, 528, 530. {{DEFAULTSORT:Aerobiological Engineering}} Category:Biological engineering Category:Ventilation Category:Human habitats --- Adapted from the Wikipedia article [Aerobiological engineering](https://en.wikipedia.org/wiki/Aerobiological_engineering) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Aerobiological_engineering?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.