Comparison of B&ES TR/19 Ductwork Cleaning Guidelines Changes Between 2005 & 2014 Editions

1. Introduction

  1. Since the introduction of TR/17 in 1998 and through subsequent TR/19 publications, the B&ES has progressively updated this guidance document, to reflect identified improvements in best practice for, cleaning, testing and verification of both general and kitchen grease extract ventilation system.

  2. In 2011 a pan European standard BS EN 15780:2011 – Ventilation for buildings – ductwork – cleanliness of ventilation systems was published. All B&ES published specifications or guidance must comply with BSI standards and thus TR/19 was updated to reflect the benchmarks and testing protocols as contained in BS EN 15780.

  3.  This report endeavours to identify the main differences between the earlier version of TR/19 and the recent updated 2013 edition published in late 2014 so that those who specify or se the guidance can clearly understand the changes which may affect their expectations on ventilation hygiene issues or managing of cleaning projects.

2. TR/19 Contents Section

2.1 In comparing the 2005 and 2013 versions this report deals with the main points of difference and does not seek to detail every change in the text.

2.2 The key differences in the contents of the two version are dealt with in more detail in later parts of this report but are summarised as follows: 

    1. Section 2 is now headed New ductwork system cleanliness which now replaces previous DW/TM 2 and 2005 guidance and gives the BS EN 15780 details in an Annex A

    2.  Section 3 - Design and access to the internal surfaces of the ventilation system gives revised guidance on access panel locations;

    3. Section 4 - Specific considerations for system components expands the range of component parts of ventilation systems;

    4. Section 5 is now System risk assessment (inspection/monitoring/testing) introduces a cleanliness quality classification for building types and introduces new test protocols and benchmarks;

    5. Section 6 - Cleaning Methods combines wet and dry method tables;

    6. Section 7 - Specific considerations for kitchen extract systems includes updated table of recommended cleaning frequencies and cleaning methods and mentions remote cleaning systems their associated risks.

    7. Section 8 - Hazardous Contamination now highlights microbiological contamination such as mould and legionella;

    8.  Section 9 - Verification of cleanliness adds new benchmark tables for new and existing ductwork based on the building cleanliness classification and sets out the testing protocols.

    9. Section10 – Health and safety draws attention to the need to refer to BS EN 12236 the standard for ductwork supports and hangers in relation the weight of a person entering the duct and its ability to support that additional load.

    10. Appendices A to H – now include the annexes from BS EN 15780 and updated guidance and test methods as well as 2 new quick reference guide tables.

3. Key Differences by Section

3.1 This part of the report deals with the main points of difference between the two Editions but excludes any general text changes.

3.2 Section 2 - New ductwork system cleanliness

3.2.1   This section states that previous DW/TM2 and TR/19 Edition 1 (2005) guidance, is replaced by Appendix F of BS EN 15780 and that this appendix is reproduced as Appendix ‘A’ of TR/19.

3.2.2 The specifier is now required to define the cleanliness quality class (CQC) of each system being installed as the level of cleanliness varies according to the type of system and building use.

3.2.3   TR/19 sets out in Table 1 (A.1) examples of building classification as shown in Appendix ‘A’ reproduced from BS EN 15780 and is shown below:

Table 1 (A.1) – Typical applications of cleanliness quality classes (for ventilation systems)

Quality Class

Typical Examples

Low

Rooms with only intermittent occupancy e.g. storage rooms, technical rooms

Medium

Offices, hotels, restaurants, schools, theatres, residential homes, shopping areas, exhibition buildings, sports buildings, general areas in hospitals and general working areas in industries

High

Laboratories, treatment areas in hospitals, high quality offices

 

3.2.4   The ultimate confirmation that a system meets the required acceptable level of dust accumulation for e new system is by means of the Preferred Vacuum Test    and Table 2 (A.4) shows the measurements for each CQC. In practice, this means it is now possible to determine if the soiling in a new system is acceptable and thus does not require cleaning prior to commissioning.

Table 2 (A.4) – Acceptable dust accumulation levels in new ductwork

Cleanliness quality class

Acceptable dust accumulation level

Supply recirculation or secondary air ductwork

Acceptable dust accumulation level

 

Extract air ductwork

Low

<0.9 g/m2

<1.8 g/m2

Medium

<0.6 g/m2

<1.8 g/m2

High

<0.3 g/m2

<0.9 g/m2

 

3.2.5   A decision flow chart (Fig.1) in TR/19 is designed to aid in the management decision making process to decide if testing is required following visual assessment and thus the need for cleaning and post clean verification.

3.2.6   The question of ductwork protection, delivery and installation (PDI) previously contained within DW/TM2 and TR/19 (2005) is now contained within Appendix ‘A’ under Table F.2 (see below), with guidance on production, delivery, site storage, installation and other considerations, in line with defined Basic Level, Intermediate Level  and Advanced Level requirements which shall be defined by the specifier.

Appendix A Table F.2 – Recommendations concerning protection, delivery and installation

PDI Level

Factory Seal

Protection during transit

Protection during site storage

Site clean

Cap off on site

Post installation clean

Basic PDI

No

No

No

No

Risers only

No #

Intermediate PDI

No

No

Yes

Yes

Yes

Not unless shown to be necessary #

Advanced PD1

Yes*

Yes*

Yes*

Yes*

Yes*

Yes

 

Notes to table F2

1. (#):   If inspection and testing indicates that cleanliness is not considered acceptable due to a failure   to meet acceptable dust accumulation levels for relevant cleanliness quality class, then despite the general guidance in the table above, cleaning would in fact be required.

2. (*)    Since the ductwork will be cleaned post-installation many costly and onerous procedures such as capping during transport can be dispensed for most installations.

3.3 Section 3 - Design and access to the internal surfaces of the ventilation                     system

3.3.1   Highlighted in this section is the need for designers to consider the need for additional loads from those who may have to enter the ductwork for cleaning and maintenance in accordance with BS EN 12236: 2002 Ventilation for buildings, ductwork, hangers and supports, Requirements for strength.

3.3.2   Sections 3.2 and 3.5 note that the ductwork contractor is only responsible under DW144 (2013) for installing access panels for inspection/servicing access to in-line equipment/components.

3.3.3   The old TR/19 Tables 1 & 2 showing access panel locations for inspection and cleaning respectively are replaced by a new Table 3 Location of Access Panels for inspection/Servicing and/or Internal Cleanliness, showing the party responsible for installing such access. Notes to Table 3 further enhance the guidance on access panel installation/location and in particular show access panels should be at a minimum of every 15 m (10m TR/19 2005), and guidance on positioning in flat oval ductwork. There is now 8 Notes to Table 3 from the previous edition.

Table 3 Location of Access Panels     for inspection/Servicing and/or Internal Cleanliness

In-line equipment

Location

Party responsible for provision of suitable access panel

Ductwork Contractor

Specialist Cleaning Contractor

Control Damper

Both Sides

Up-stream panel

Down-stream panel

Fire Dampers

Both Sides

To suit damper maintenance

Opposite side

Heating/cooling/re-claim Coils

Both Sides

Panel on both sides

 

Attenuators (Rectangular)

Both Sides

Up-stream panel

Down-stream panel

Attenuators (Circular)

Both Sides

Up-stream panel

Down-stream panel

Filter sections

Both Sides

Up-stream panel

Down-stream panel

Air turning vanes

Both Sides

Up-stream panel

Down-stream panel

Changes of direction

One side

 

One panel to suit

In-duct fans/devices

Both Sides

Up-stream panel

Down-stream panel

Inlet/exhaust louvre

One side

One panel to suit

 

Intermediate cleaning panels

 

 

To suite frequency specified in TR19 and DW/172

 

3.3.4   Tables 4 and 5 have changes to the duct sizes and the commensurate access panel dimensions, the tables below show the current guidance with the previous edition dimensions in brackets.

Table 4 Recommended size of openings (rectangular & flat oval)

Duct size up to longest size major axis

Recommended dimensions of openings

200 mm

300 mm (500 mm)

400 mm (1000 mm)

>500 mm (duct entry) 

300 mm

300 mm (400 mm)

450 mm

450 mm (600 mm)

150 mm (100mm)

200 mm

300 mm (450 mm)

450 mm (500 mm)

 

Table 5 Recommended size of opening (circular)

Duct size up to

Recommended dimensions of openings

310 mm (315 mm)

450 mm (500 mm)

550 mm (1000 mm)

>600 mm (duct entry)

250 mm (300 mm)

400 mm

400 mm

500 mm (600 mm)

150 mm (100 mm)

300 mm (200 mm)

300 mm (450 mm)

400 mm (500 mm)

 

Note to tables 3, 4 & 5

1.  For ductwork in dimensions unsuited for mechanised cleaning and where human access is needed, the type and location of access components shall allow the cleaning person to safely and without hindrance enter and exit the ducts (ref: BS EN 12097)

3.4 Section 4 - Specific considerations for system components

3.4.1   Wording to the original sections has been amended in some cases but the main changes cover the addition of:

  1. Phenolic Ductwork;

  2. Glass Fibre Reinforced (GRP) Ductwork;

  3. Air Socks

  4. Chilled Beams; and

  5. Fire Clad & Fire Rated Ductwork

3.5 Section 5 – System risk assessment (inspection/monitoring/testing)

3.5.1   This section contains the most significant changes to the previous edition, as it includes:

  • updated ACOPS from Regulations;

  • monitoring and inspection frequencies;

  • identification and assessment of risk;

  • new testing protocols; and

  • benchmarks for acceptable contamination of existing ductwork

3.5.2   With the updating of the Workplace (Health, Safety and Welfare) Regulations in 2013, TR19 new edition now includes ACOP’s 41, 42 and 52 from the Regulations 5 & 6.

3.5.3   Importance is now placed on specifying monitoring and inspection frequencies   rather than cleaning frequencies as, a system found to have unacceptable levels of contamination, found during inspection may alter the frequency of cleaning, where specified (kitchen extract system cleaning frequencies are dealt with in Section 7).

3.5.4   The inclusion of Table 6 Recommended minimum regular inspection/monitoring intervals (in months) according to SQC (See below), taken from BS EN 15780   now gives guidance on how often systems should be assessed from their hygienic condition.

Table 6 Recommended minimum regular inspection/monitoring intervals (in months) according to system (cleanliness) quality class (‘SQC’)

SQC

Inspection and Testing Intervals (months)

      AHU            Filters(2)             Wet areas(1)              Ducts         Terminals

Low

       24                 12                         12                            48                  48

Medium

       12                 12                           6                            24(3)               24(3)     

High

       12                  6                            6                           12(4)               12(4)

 

Notes to Table 6

  1. Wet areas of the ventilation system comprise humidification, cooling coils, condensate trays and other ancillary or associated items of plant containing these elements.

  2. Filters should be inspected and maintained in according to the manufacturer’s recommendations, with these intervals as a minimum.

  3. For compliance with HTM03, this frequency should be increased to 12 monthly.

  4. For compliance with HTM03, this frequency should be increased to 3 monthly.

3.5.5   The Testing Procedures section gives the Preferred Vacuum Test (PVT) as recommended in BS EN 15780 and the Deposit Thickness Test (DTT) from previous TR19 editions.

3.5.6   The PVT requires the weighing of cassette filters usually undertaken by an approved laboratory, with a delayed notice of results.

3.5.7   By contrast DTT is carried with the results available at the time of testing, giving the client early notification of the results.

3.5.8   The inclusion of Table 7 Acceptable Contamination Levels in Existing Ductwork (see below), with benchmarks for both PVT and DTT results allows the specifier to choose the test method for system cleanliness evaluation and monitoring. It should be noted that the only method acceptable for validation following duct cleaning is the PVT as detailed in Section 9.

Table 7 Acceptable Contamination Levels in Existing Ductwork

System Quality Class

Acceptable Contamination Levels – Supply Ductwork

Acceptable Contamination Levels – Re-Circulation or Secondary Air Ductwork

Acceptable Contamination Levels – Extract Ductwork

 

D.T.T

P.V.T

D.T.T

P.V.T

D.T.T

P.V.T

Low

90µm

<4.5g/m2

120µm

<6.0g/m2

180µm

<9.0g/m2

Medium

60µm

<3.0g/m2

90µm

<4.5g/m2

180µm

<9.0g/m2

High

12µm

<0.6g/m2

60µm

<43.0g/m2

180µm

<9.0g/m2

 

Notes to Table 7

            1. Prior to using this table a definition of the relevant ventilation system(s) cleanliness quality class(es) should be decided.

            2. The table should be used to define when it is considered appropriate to clean the system(s) using either the preferred vacuum testing (PVT) or deposit thickness testing (DTT) measurement methods.

            3. In the case of any extract system direct to atmosphere a reduction of airflow by 15% or more would equally define the need to clean the system.

3.6 Section 6 - Cleaning Methods

3.6.1   This section does not radically change any cleaning method that may be chosen either individual or in combination with other methods. It does however expand on some considerations when choosing the cleaning method and combine the previous Tables 6 and 7 into a new Table 8 Cleaning Methods (see below) which shows mechanical, manual and wet cleaning categories.

Table 8 Cleaning Methods

 

Generic Name

Energy Source

Method of removing deposit

Typical Application

Mechanical

Rotary Brushing

Compressed air and/or electricity

Brushing the surface of the ductwork using mechanical action

Dry deposits that in some places could require agitation to remove from the ductwork surfaces

Air Whip/Nozzle

Compressed air

Directional jet nozzle on the end of a flexible hose

Dry, loose deposits. Not to be used where cross contamination could be an issue

Air Lance

Compressed air

Air gun with a trigger/ lance that can be used to direct compressed air locally

Internal coils/linear diffusers

Manual

Hand wipe

Manual

Wiping the surface using a medium appropriate to the purpose

Ultra clean environments

Hand scrape

Manual

Removing heavy deposits by hand scraping

Strongly adhered deposits in areas where arm or man access is possible

Hand brushing

Manual

Sweeping the surface using an appropriate brush and collection device

Heavy, loose deposits in areas where arm or man access is possible

Hand vacuum

Electricity/Manual

Removal of deposits by means of vacuum

Loose deposits in areas where arm or man access is possible

Wet

Wet vacuum

Electricity/Manual

Removing of liquid by means of wet vacuum

AHU’s/humidification chambers

Chemical clean

Mechanical/ Manual

Application of a suitable chemicals to soften or dissolve deposits

Gross soiling

Hand wash/wipe

Manual

Washing the surface using an appropriate cleaning agent

Large AHU’s, air intake plenums etc. and grease laden surfaces

Steam/High pressure water wash

Electricity

High pressure system used to dislodge/dissolve deposits

Concrete intake plenums and grease laden surfaces

 

3.7 Section 7 - Specific considerations for kitchen extract systems

3.7.1   The sections 7.1 to 7.14 deal with and expand the guidance from the previous version by including reference to the Regulatory Reform (Fire Safety) Order 2005, COSHH regulations and FPA insurance guidance contained in Appendices C and H.

3.7.2   Access panel guidance is largely the same as the earlier edition Table 8 but a new Table 9 Location of access panels for cleaning and inspection purposes (see below) includes new guidance by recommending risers have panels at a maximum of 3m centres. In additional the Notes to Table 9 include 8 sections with improved guidance.

Table 9 Location of access panels for cleaning and inspection purposes

Volume control dampers

Both sides

Fire dampers

Both sides (see Note 7)

Attenuators

Both sides

Changes in direction

Both sides

Filter sections

Both sides

Horizontal ducts

Generally 3m centres (see Note 2)

Risers

Maximum 3m centres (see Note3)

Extract fans

Both sides (see Note 4)

Discharge grille/mesh

One side (see Note 6)

Notes to Table 9

      1. Additional builders work hatches may need to be fitted in ceilings/walls in existing installations, or provided for in new constructions. These would not be provided for by the cleaning contractor unless a separately specified cost is provided.

      2. Access opening for cleaning purposes are generally required at a maximum of 3 meter centres and or at each change of direction where head and should access is possible. This should be reduced where the size of the duct prevents adequate cleaning by hand, where there are several changes of direction or where external features restrict the positioning of panels.

      3. Internal kitchen extract risers often require access panels fitted at maximum 3 meter centres on each floor level so that the internal surfaces can be reached and fire dampers, where fitted, cleaned and checked. In some buildings this may require  additional builders work (e.g. hatches through brickwork) to reach riser ducts (see note 1 above and 7.17). The exception to this may be if abseil cleaning is practicable, where specialist advice should be sought. In such cases it may be possible to reduce the quantity of access panels.

      4. Extract fan design should allow thorough cleaning of impellor blades and internal surfaces without the need for dismantling, i.e. ductwork with access panels should be provided immediately upstream and downstream. Larger fans should be designed with panels in the casing. Similarly, attenuators or other in-line fittings likely to obscure cleaning activity should be provided with access both sides.

      5. Guideline access frequency given above may be reduce where safe personnel entry can be adequately applied. However, in all instances every section of ductwork should be capable of verification inspection.

      6. Design consideration should be given to the provision of safe access to the down-stream side of discharge grilles, bird guard mesh and louvres.

      7. Fire dampers should not be fitted in new installations in accordance with BS5588, but may still be found in older systems.

      8. The designer should clearly specify the locations, sizes and responsibility for access door installation to facilitate regular access for fire safety cleaning.

3.7.3  Examples of cleaning methodology are now contained in Table 10 (see below) which no longer includes ‘Blasting (remote or direct) using suitable medium as appropriate’. The remaining methods are the same with variations on some minor wording. The notes to Table 10 refer to new technology such as ‘brush and foam chemical’ methods, with a warning on leakages and a recommendation that they should not be used above false ceilings.

3.7.4  Use of chemicals is also highlighted as to the possible effects on the duct fabric, components and/or those applying the chemical.

Table 10 Examples of cleaning methodology

Generic name

Energy source

Removal method

Hand wipe

Manual

Wiping the surface of the ductwork

Hand scrape

Manual

Removing heavy deposits by hand scraping

Chemical

Manual

Softens or dissolves deposits making them suitable for hand scraping

Steam cleaning

Electrical

Hot vapour expelled at high pressure from lance to dislodge/dissolve deposits

High pressure water washing

Electrical

Water expelled at high pressure from lance or nozzle to dislodge deposits

 

Notes to Table 10

  1. The above listed methods are considered normal best practice methods, however these are not exhaustive. New technology such as ‘brush and foam chemical’ methods are available and in some instances can be successful. It is critical that the cleanliness result can be verified by post-clean evidence.

  2. Remote cleaning methods are not generally use for cleaning grease extract ductwork systems. The reason for this is the type of grease that is typically deposited within kitchen extract systems will not normally be released by remote mechanical means as effectively as manual methods.

  3. Remote chemical brushing, steam cleaning and high pressure water washing are not recommended for ductwork that is situated above false ceilings or in sensitive areas, due to possible leakage of contaminants from the duct, unless specifically designed for wet cleaning.

  4. After applying wet cleaning methods care should be taken to ensure that any condensed vapours and cleaning fluids are removed from all parts of the system.

  5. The use of chemical cleaning agents should only be considered where risk/COSHH assessment has been carried out (see section 10), the details recorded and the effects of the applied chemicals have been assessed on material construction, environment and for hazards to cleaning personnel.

  6. It should be noted that it is not normally economically practicable to clean kitchen extract systems and fans to a “like new” bright metal condition due to substrate staining. Care should be taken to avoid damage or removal of protective coatings on fan casings, impellors and motor housings. 

3.7.5  The significant change to this section is the change to the  recommendations and frequency of cleaning, with a new risk assessment matrix in Table 11 Kitchen grease extract systems (see below). This now incorporates low, medium and high grease production categories and four daily usage bands to the original three bands. This now assists specifiers in choosing a frequency of cleaning that more closely matches their cooking styles and daily usage.

 

Table 11 Kitchen grease extract systems

Perceived level of grease production

Typical Example

Cleaning intervals (months)

Daily usage

Up to 6 hours

6-12 hours

12-16 hours

16+ hours

Low

No significant production of grease laden aerosols during normal daily food production operations

12

12

6

6

Medium

Moderate production of grease laden aerosols during normal daily food production operations

12

6

4

3

High

Heavy significant or continual production of grease laden aerosols during normal daily food production operations

6

3

3

2

 

Note to Table 11

  1. Commercial liability/property insurance policies invariably contain conditions and warranties that stipulate a minimum cleaning frequency for grease extract ductwork systems under the insurance contract which can be a higher frequency of cleaning than TR/19 recommendations. Failure to comply with such requirements will invalidate the property insurance policy.

  2. The canopy and canopy/extract plenum is an area of higher fire risk and consideration should be given to more frequent cleaning in accordance with insurer’s requirements.

  3. Periodic specialist cleaning should be accompanied by daily or weekly cleaning of canopies, filters and associated drains and traps in accordance with manufacturers’ recommendations, typically carried out by the kitchen operator, in compliance with the property insurers’ requirements.

3.7.6  Post Clean Verification in both editions remain mainly the same with the previous edition Table 9 replaced by Table 12 Surface grease deposit limits Notes to Table 12 remain largely  the same as for the previous edition.

3.7.7  Testing protocols remain the same in both editions as do the requirements for the post clean report contents.

3.7.8  Recognising that some specifiers may conclude, following a risk assessment, that their extract system qualifies as a Local Exhaust Ventilation (LEV) system under COSHH regulations, users are now referred to HSG258 for thorough examination and testing requirements in the new edition.

3.8 Section 8 – Hazardous Contamination

3.8.1  The guidance in this section from previous and current editions is broadly the same with some minor additions in the new edition. However, whereas the previous edition had in Appendix A, guidance on Microbiological Contamination, the new edition has updated guidance to include CIBSE TM26 test protocols.

3.9 Section 9 – Verification of cleanliness

3.9.1  This section now deals with acceptable levels of dust accumulation in newly installed ductwork as well as the acceptable level of dust accumulation following a cleaning operation.

3.9.2   After cleaning of ductwork the only test to verify acceptable levels of soiling is the PVT and that the benchmark for acceptable post-clean levels is < 0.3 g/m2. The previous edition required the NADCA style vacuum test to verify post-clean levels.

3.9.2   Timing of post-clean testing and the content of the completion report remain the same in both editions.

3.10 Section 10 – Health and Safety

3.10.1 The new edition broadly reflects the guidance given in the previous edition, with new emphasis on the need for duct supports capable of taking additional weight from duct entry in line with BS EN 12236:2002.

3.11 Appendices A – H

3.11.1  In these Appendices extracts from BS EN 15780 and CIBSE TM26 are reproduced. In addition recent changes in legislation and guidance is now shown in the new edition.

3.11.2  Appendix D Cleaning Contractor Selection is broadly the same, now mentioning the EVHA as an acceptable association for affiliation.

3.11.3   Appendix E Testing Methods now covers the protocols foe DTT, PVT and WFTT and the sampling and analysis procedures.

3.11.4   PVT requires that a new shape test area template is used and that a small 5 cm length suction tube is attached to the inlet side of the filter cassette, to scrape across the entire template test area.

3.11.5   PVT also requires that the flow rate is increased from 10.0 l/min (previous standard) to 15.0 l/min.

3.11.6   Appendix F is a new Quick Guide 1: Air Ductwork Systems incorporating building Cleanliness Quality Classifications, acceptable contamination levels, post clean verification levels and inspection and testing intervals. This provides a one stop reference covering all the new requirements for specifiers and contractors alike.

3.11.7   Appendix G a Quick Guide 2: Kitchen Grease Extract Systems gives a single reference on grease production levels, cleaning intervals, inspection intervals, routine testing limits and post clean testing limits.

4.0 Summary

Much of the previous edition has been transferred to the new edition, but the new guidance set out in BS EN 15780 has significantly changed the guidance on general supply and extract systems, now included in the new TR/19. The introduction of a CQC, testing protocol and test equipment specification.

Separation of new duct systems from existing systems and their attendant benchmarks now give specifiers and installer’s clearer guidance on acceptable dust accumulations.

Kitchen grease extract cleaning guidance is not affected by BS EN 15780 as this is not included in that guidance. However, the introduction of the RRFSO has highlighted the need for greater guidance for those responsible for fire safety in premises. The quick guide in Appendix G sets out in one section the options in identifying grease production, usage and recommended cleaning frequencies as well as the test benchmarks.

Changes to DW/144 is updated in the guidance, with for the first time clearly defined responsibilities, for installing access panels on new installations.