TB040-air-duct-cleanliness-inspection-and-sampling-locations-mv2-tb040

TECHNICAL BULLETINAIR DUCT CLEANLINESS INSPECTION AND SAMPLINGLOCATIONS ON EXISTING DUCTWORK SYSTEMSThe objective of this technical bulletin is to describe good practice in determining the number and locationof cleanliness sampling points when carrying out inspections of air duct systems according to BESA Guide toGood Practice TR19: Internal Cleanliness of Ventilation Systems (2013).1. TECHNICAL INFORMATION TR19 Section 5 System Risk Assessment (Inspection/Monitoring) describes the scope of a risk assessment to establish whether an existing air duct system (in maintenance) requires cleaning. It calls for a minimum of 3 locations per system and describes the components and the selection of parts of ductwork which should be included in an inspection. TR19 Section 9 Verification of Cleanliness describes the methods to determine whether an air duct system has been cleaned, or if a newly installed air duct system, is acceptably clean i.e. ‘post-clean verification’ and ‘acceptance testing’. For air duct systems, TR19 Guide to Good Practice calls for agreement between the client/specifier and the inspector as to how many samples should be taken and their location. This bulletin is intended to advise what good practice is in the absence of such a specific agreement. BESA SFG20 Building Services Maintenance Standard Core element 17.01: ‘Ductwork Cleaning – Hygiene, Inspections & Monitoring’ calls for inspection and testing of duct system cleanliness according to TR19. The Workplace (Health, Safety & Welfare) Regulations L24 (2013) states that “Mechanical ventilation systems (including air conditioning systems) should be regularly and adequately cleaned. They should also be properly tested and maintained to ensure that they are kept clean and free from anything which may contaminate the air.” TR19 Sections 7.32-7.41 on Specific Considerations for Kitchen Extract Systems are more prescriptive as to the frequency and location of inspection and measurement sites within a grease extract system. It is therefore not necessary to include kitchen extract in the scope of this Technical Bulletin. Further guidance is given in TB/009.2. IMPLEMENTATION OF GOOD PRACTICEA system inspection should include sufficient sampling and inspection locations so that itis properly representative of all conditions within the system.Demonstrably reasonable and prudent judgements must be made in the selection ofinspection locations.TR19 Section 5.7 details system inspection locations which include traditional plant Figure 1 Deposit Thickness Testinglocations such as fresh air intake, filters, heat exchangers etc. However the key point isTB/040 1 of 2

AIR DUCT CLEANLINESS INSPECTION AND SAMPLING LOCATIONSTB/040 to ensure representative inspection of ductwork locations as these are not normally viewed during regular mechanical maintenance operations.WHERE TO INSPECT DUCTWORK?As a minimum: duct inspections should be spread across a system, e.g. beginning, middle and end. This spread should be bothhorizontal along the length of a duct sub-system running across a floor, and vertical at selected locations from higher and lowerfloors if applicable. Care should be taken to ensure that inspection locations are demonstrably representative. Within a system,sample should be taken as a minimum: 1 at the intake duct, 1 per air handling unit/fan, 1 per distribution duct to plant roomand 1 per floor (or every 250m on each level).It is not good practice to limit duct inspections only to e.g. a plant room, or at the beginning of floor duct runs off a riser whichare typically the most easily accessible ductwork, since these areas can be unrepresentative of fouling in ductwork furtherdownstream.TESTING METHODOLOGYInspection on existing ductwork systems can be carried out by either Preferred Vacuum Testing (PVT) or Deposit ThicknessTesting (DTT). Guidance on how to carry these out and equipment needed can be found in TR19. When inpecting newlyinstalled systems only PVT is suitable as per TR19.MAINTENANCE MONITORING VS POST-CLEAN Figure 2 Preferred Vacuum TestingIdeal sampling locations can more easily be selected and accessed during post-clean verification since access to the ductwork, is readily available. Inmaintenance situations with ongoing occupation, the inspector mustminimize disruption and take occupancy into account. However, an absenceof suitable access for duct inspections would be regarded as a defect to beremedied. LARGE SYSTEMS In large duct systems, defined as > 500m linear, 3 duct inspection locations (as a minimum) at the beginning, middle and end, will typically be insufficient to be reasonably representative. It is therefore good practice to add further inspection locations per 250m linear. In this way, a system of 501-1000m linear would be inspected at minimum 5 locations and 1001-1500m at 7 locations.For any queries, please contact the technical helpline at [email protected] or call 0207 313 4927.Images provided courtesy of Craig Booth Associates and Ventilation Surveys and Services Ltd.Note: this document is based on knowledge available at the time of publication and is meant for general purposes, not for reliance on in relation to specifictechnical or legal issues, in which case you should always seek independent advice. No responsibility of any kind for any injury, death, loss, damage or delayhowever caused, resulting from the use of the advice and recommendations contained herein, is accepted by the authors or others involved in its publication(including the Building & Engineering Services Association). 06/09/2017 TB/0XX 2 of 2