Impact of Air-Conditioning Filters on Microbial Growth and Indoor Air Pollution

Abstract

Contemporary lifestyles dictate that people spend between 60 and 90% of their daily lives indoors. For those living in warm climates, air conditioning is thus considered a necessity. Air conditioners function by removing hot and humid air from building interior and replacing it with cooler air. Microorganisms are considered among the most important sources of poor quality of indoor air, and contamination of this air by microbial pollutants is being increasingly recognized as a public health problem and a probable cause of the so-called sick building syndrome. In this regard, microfiber glass panel filters are considered to provide an effective solution for air filtration and have been demonstrated to improve air quality in many applications. However, recent research has demonstrated that certain microorganisms are able to colonize panel filter surfaces. Studies on selected microbes isolated from the most commonly used filters have revealed that the bacterial and fungal moist masses carried on sponge-type filters are greater than those carried on polyester and high-efficiency particulate air (HEPA) filters. Moreover, microbial moist mass has been found to increase with increasing incubation time. In addition, recent research has shown that certain microorganisms, particularly fungi, can colonize the materials used in heating, ventilation, and airconditioning systems (HVAC).

Susceptibility of Bacteria Isolated from Air-Conditioning System Ducts to Different Ultraviolet Radiation Doses

“…Six species of bacteria (S. liquefaciens, S. lentus, B. subtilis, B. cereus, O. ureolytica, and B. pumilus), which were the most abundant bacteria in the AC duct, were isolated during the summer season in 2009, from air conditioning systems (homes, schools, hospitals, and shopping centers) in the eastern region of Saudi Arabia (Al-abdalall and Al-abkari 2017: Al-abdalall et al 2019) [16][17] , and cultured on nutrient agar media for 24 h at 37°C. Bacterial isolates were preserved purely on NA slants.…”

An overview of solutions for airborne viral transmission reduction related to HVAC systems including liquid desiccant air-scrubbing

“…The increase in ΔP fan may not be accommodated by the majority of the HVAC systems, resulting in being complex for retrofitting [ 1 ], and is not recommended for use in public transports, because it would be detrimental for the HVAC equipment. In addition, filters also represent a site of accumulation and amplification of microorganisms [ 11 , 59 ], which results in a decrease in the efficiency of the filter and in its deterioration [ 38 ], requiring high maintenance costs [ 65 ]. As such, HEPA filters are not commonly used in commercial or residential buildings but only for specific applications, such as in healthcare facilities or airplanes [ 21 ], and are not further considered in the case study of Section 6.2 .…”

An overview of solutions for airborne viral transmission reduction related to HVAC systems including liquid desiccant air-scrubbing

“…The increase in ΔPfan may not be accommodated by the majority of the HVAC systems, resulting in being complex for retrofitting [1], and is not recommended for use in public transports, because it would be detrimental for the HVAC equipment. In addition, filters also represent a site of accumulation and amplification of microorganisms [11,138], which results in a decrease in the efficiency of the filter and in its deterioration [116], requiring high maintenance costs [45]. As such, HEPA filters are not commonly used in commercial or residential buildings but only for specific applications, such as in healthcare facilities or airplanes [35], and are not further considered in the case study of Section 5.2.…”

“…Efficiency of various filters of HVAC systems for different particle sizes and related application, adapted from[138][139][140].…”