Air Ventilation

Ventilation systems by their very nature will accumulate contamination the degree of which will be influenced by the quality of the incoming air, filtration, design, maintenance and usage. Over time varying types of contamination will accumulate to levels which may detrimentally influence the quality of the supplied air and hence may affect the health of building users. Contaminant levels can build to such an extent that they provide the added risk of fire propagation.

The proper maintenance of a ventilation system is recognised as crucial to the health, economic and safe operation of occupied spaces. To ensure compliance with the Regulations and associated Approved Code of Practice from the Health and Safety Commission which states that all mechanical ventilation systems should be regularly and properly cleaned, tested and maintained to ensure that they are kept clean and free from anything which may contaminate the air.

The Workplace (Health, Safety and Welfare) Regulation 1992 requires that effective provision should be made to ensure that every enclosed workplace is ventilated by a sufficient quantity of fresh or purified air. Where this ventilation is provided by mechanical means the regulations requires mechanical ventilation systems to be maintained (including cleaned as appropriate) in efficient working order.

To be compliant with TR/19, ventilation supply and extract ductwork must be classified at one of three levels, according to the area of the building that it serves. Each system must be classified as high, medium or low, in order to reflect the purpose and function of that area of the property.

System Quality Class (SQC)
Low – Rooms with only intermittent occupancy, e.g. storage rooms
Medium – Offices, hotels, restaurants, schools, theatres, residential homes, shopping areas, exhibition buildings, sport buildings, general areas in hospitals, general working areas in industries
High – Laboratories, treatment areas in hospitals, high quality offices

Recommended minimum regular inspection/monitoring intervals (in months) according to system quality class (‘SQC’) Inspection and Testing Intervals (months)
Low – SQC 24 – AHU 12 – Filters (2) 6 Ducts – 48 Terminals – 48
Medium – SQC 12 – AHU 12 – Filters (2) 6 Ducts – 24(3) Terminals – 24(3)
High – SQC 12 – AHU 6 – Filters (2) 6 Ducts – 12(4) Terminals – 12(4)

The assessment frequencies above should be considered as the minimum recommendations and the necessity of increasing them will depend on the environment conditions, on the activity and on mechanical and human conditions in both building and its surroundings.

To obtain satisfactory conditions of cleanliness, all the components associated with the ventilation system should be included.

A suitable and sufficient risk assessment is required to identify and assess the risk of contamination levels in a ventilation system. Precautionary measures to reduce risk should be identified and remedial measures put into action.


  • A ventilation system inspection should include sufficient sampling and inspection locations so that it is properly representative of all conditions within the system.
  • Demonstrably reasonable and prudent judgements must be made in the selection of inspection locations.
  • TR19 details system inspection locations which include traditional plant locations such as fresh air intake, filters, heat exchangers etc. The key point is to ensure representative inspection of ductwork locations as these are not normally viewed during regular mechanical maintenance operations.

Inspection on existing ductwork systems is carried out using the Deposit Thickness Testing (DTT).

As a minimum: duct inspections should be spread across a system, e.g. beginning, middle and end. This spread should be both horizontal along the length of a duct sub-system running across a floor, and vertical at selected locations from higher and lower floors if applicable.

Many existing ventilation systems have insufficient access points to enable cleaning; Hyperklean will install access doors at strategic points throughout the system to enable regular inspection and cleaning.

All works are fully certified and post clean reports provided.

Please don’t hesitate to get in touch if you’d like a free quote or if we can be of any assistance: contact us or via live chat or telephone.

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