**8. Conclusion**

Microbial pollution is one of the most fundamental indoor environmental quality problems in buildings. Therefore, this chapter has presented several solutions for indoor air quality monitoring in an effort to enhance the healthcare by describing the potential impact of HVAC systems on the indoor air quality. The principles of air filtration and traditional air filter types were presented.

Also, the chapter covered the filtration technology and the indoor air quality topics. Subsequently, the air duct cleaning devices, mold formation, and HVAC systems and indoor pollution were illustrated. Moreover, this chapter provided the ASHRAE standards, which was used to select the suitable HVAC filters. The six most common designs of HVAC filters were briefly described. This chapter was followed by the modern filters. All advanced air filters, UV lights, activated carbon, deodorizing, antibacterial, electrostatic and HEPA filters, microbial filtration efficiency of HEPA filters were discussed extensively.

A brief description of the microbial colonization on the commonly used traditional filter types for air-conditioning systems were provided, followed by a detailed explanation of the relationship between traditional filters and microbe's formation.

Even though there is highly development in designing advanced filters to overcome microbial pollution, we are still facing indoor air pollution problems. The most challenging step is providing an affordable construction, easy to install, made of environmentally friendly and long-term materials, available in different designs and able to avoid the existence of microbial growth.
