Ventilation cleaning

Most people spend 80-90% of their time indoor. More and more employers are aware today of the losses which may be occasioned by their employees taking sick leaves. Apart from poorer productivity and efficiency outcomes, this involves loss of serious money as well. Many research papers have shown that contamination of workplace rooms tends to originate from ventilation and air conditioning systems.

Internal surface area of ventilation ducts in contemporary buildings is estimated at around 10% of the total floor area. Floors are cleaned, fresh air is clean, refreshing, oxygen-rich, while ventilation ducts will sometimes be left without cleaning throughout the life of the building!

The more complex the ventilation system, the higher the probability of occurrence of problems. Dust, microorganisms, remnants of construction materials and other contaminants may turn air supply ducts into sources of hazardous substances, such as fungi, insulation components, odors, and organic particles. Apart from health and hygienic issues, ventilation system contamination may lead to higher energy consumption, costs of cleaning, elevated risk of corrosion and clogging of fire dampers.

Extensive research shows that hazards for human life are more severe in the case of air conditioned buildings than other buildings.

Contamination of ventilation and air conditioning ducts may be a source of hazardous substances and may cause various symptoms of illness to occur in people occupying the building. Moreover, it has been proven that inadequate maintenance work is the most frequent source of problems.

There are three main reasons for cleaning air conditioning and ventilation systems:

  • to achieve the designed service values of air handling and transmission units - suspended dust depositing on internal surfaces of ventilation ducts and external surfaces of air handling equipment will cause, among other issues, higher air flow resistance and simultaneous decrease of air supply flow,
  • to eliminate or, in the worst case scenario, to mitigate the risk of fire and explosion - in case of flammable and explosive contaminants deposition inside installation ducts - in office buildings, this problem is most common in kitchen systems,
  • to ensure such indoor conditions that will not adversely affect the health of occupants - consequence of breathing contaminated air.

Therefore, every system installation should be covered by a quality maintenance program and therefore subject to regular inspection and cleaning. The following elements are typically inspected and maintained:

  • Air intakes
  • Filters
  • Fans and driving belts
  • Plenum chambers
  • Heating and cooling coils
  • Humidifiers
  • Fire dampers
  • Flow control dampers
  • Rotating blades
  • Insulation
  • Diffusers
  • Outlet grilles
  • Outlet ducts

A decision to proceed with cleaning the installation is usually taken after visual inspection of purity of system interiors. No available publication would specify the mandatory frequency of cleaning installations because cleaning times cannot be set arbitrarily, without prior audit of each system's condition, due to system service in highly variable conditions (with different outside air purity levels, quantity and efficiency of installed air filters, care about the system condition by personnel in charge of service and maintenance). Thus, another question arises: when should you check the hygienic condition of your installation, and how to determine whether your installation is still clean or it should be considered contaminated and requiring cleaning. European countries have adopted the requirements prescribed by U.S. NADCA (National Air Duct Cleaners Association) standards. The table below presents the recommended ventilation duct inspection frequency for different categories of buildings.

Building classificationBuilding typeVentilation and/or air conditioning AHUAir supply ductsRecirculation, exhaust ducts
Class 1Industrial building1 year1 year1 year
Class 2Residential building1 year2 years2 years
Class 3Light commercial building1 year2 years2 years
Class 4Commercial building1 year2 years2 years
Class 5Healthcare buildings1 year1 year1 year
Class 6Shipbuilding1 year2 years2 years
Class 7Special purpose areas***

* - Requirements to be set by the building's user

In Poland, the following provisions of the Building Code should be followed:

    Article 62.1 Buildings and other civil structures should be subject to the following actions taken by their owner or manager during their useful life:

  • 1) regular inspection, at least once a year, consisting of checking the technical adequacy of:
  • a. elements of buildings, civil structures and systems exposed to harmful weather impacts and damaging effects of factors occurring during the life of the building,
  • 2) regular inspection, at least once every 5 years, consisting of checking the service condition and functional quality of the entire building or structure, the appearance of the facility and its surroundings, (...).

The purpose of ventilation ducts inspection shall be to verify the level of contamination. Comparative method is the best method to determine the level of contamination. An overview table presenting different duct contamination levels is used for this purpose.

Out of sight!

Floors in office rooms are cleaned once a week on average; however, ventilation ducts that are supposed to supply healthy, oxygen-rich, fresh air, may be left without cleaning throughout the life of the building!

40 % of contaminants in indoor air comes from air supplied by ventilation systems.

Why should we clean ventilation systems?

It has been proven that ventilation and air conditioning systems are places where contaminants potentially capable of affecting human health gather, such as mold, fungi, bacteria, dust and powders. Removal of these contaminants from ventilation systems should be considered as one of the elements of the general action aimed at improving the quality of indoor air.

Clean and functional systems are less prone to failure, have longer lives and work more efficiently than contaminated ones. Due to flammable materials depositing in ventilation ducts, fire hazards will occur. Oil and grease from kitchen installations, clothing fibers, etc. may be easily transferred to ventilation ducts. In such buildings, cleaning ventilation ducts eliminates or, in the worst case scenario, mitigates the risk of explosion and fire.

Microbiological testing

Apart from video inspection, additional microbiological analysis may be necessary, due to frequent occurrence of bacteria and pathogenic fungi in ventilation systems.