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Toronto and Area's Asbestos, Indoor Air Quality and Mold Inspection Professionals


Maintaining clean heating, ventilation and air-conditioning (HVAC) systems is an important part of sustaining acceptable indoor air quality (IAQ). When an HVAC system is a source of contaminants introduced into the occupied spaces, properly performed system cleaning services should take place to reduce or eliminate contaminate introduction.

Contaminates in HVAC systems may take many forms. Common contaminates include dust particles, active bacterial or fungal growth, debris from rusted HVAC component, man-made vitreous fibers, mold spores, and other items.

Our Experience has shown that very few (if any) HVAC systems are free of all particulate. In fact, particle deposition on component surfaces starts before the HVAC system is even installed. Airborne particles in factory settings and assembly areas are likely to settle on air-handling components and fiberglass insulation, as well as adhere to the surface of metal components.

The original installation process will subject the HVAC system to even more contamination. Construction sites contain significant amounts of airborne concrete dust, gypsum dust, sand particles, biological particulate aerosols and many other airborne contaminates in the ambient air. There particles often settle on or within the HVAC system during construction.

After the HVAC system is installed ands its operation begins, the particulate accumulation process continues throughout the life of the system. Poor design, installation and maintenance practices, low-efficiency air filtration, airflow bypass, inadequate or infrequent preventative maintenance practices, humid conditions, and many other factors will result in contaminated HVAC systems. HVAC systems may also serve to transport and redistribute unwanted particles from other sources in the building.

HVAC cleaning services have been available since the early 1900’s. However, it was not until the 1970s that growing public concern for better indoor air quality (IAQ) led to an understanding of the importance of cleaning HVAC system components. Public awareness has increased ever since.

Determining the Need for HVAC System cleaning and Restoration

It is highly recommender that HVAC systems be cleaned when an HVAC cleanliness inspection indicates that the system is contaminated with a significant accumulation of particulate or if microbial contamination either Condition 2 or Condition 3. If the preliminary inspection shows that HVAC system performance is compromised due to contamination build-up, cleaning is highly recommended.

Condition 2 (settled spores and trace growth): An indoor environment, which is primarily contaminated with settled spores that were dispersed directly or indirectly from a condition 3 area, and which may have traces of actual growth.

Condition 3 (actual growth): An indoor environment contaminated with the presence of actual mold growth and associated spores. Actual growth includes growth that is active or dormant, visible or hidden.

Often HVAC system components collect significant amounts of debris and particulate during construction activities within a building. It is highly recommended that newly installed HVAC systems or HVAC systems undergoing renovations be verified for cleanliness, and further protected before the system is permitted to operate. It is highly recommended that consistent HVAC system inspections be part of a buildings overall indoor air quality management program.

Table 1 HVAC Cleanliness Inspection Schedule(Recommended Intervals)


HVAC Cleanliness Inspection Schedule

HVAC systems should be routinely inspected for cleanliness by visual inspection. Table 1 provides a recommended inspection schedule for major HVAC system components within different building use classifications. The inspection intervals classified in table 1 are only minimum recommendations. The need for more frequent cleanliness inspections is subject to numerous environmental, mechanical and human factors. Geographic regions with a higher level of humidity, will warrant HVAC system inspections on a more frequent basis, due to increased potential for microbial amplification.