New British Standard on ventilation systems ductwork cleanliness: the implications for health estates
by Andrew Steel, Managing Director, Airmec
This article was first published in The HefmA Pulse, Vol 20, October 2013
http://www.hefma.co.uk/the-hefma-pulse
The introduction of a new British Standard for cleanliness levels in ductwork has a number of significant implications for Health Estate professionals. BS EN 15780:2011 Ventilation for buildings – Ductwork – Cleanliness of ventilation systems clearly defines vital goals to be achieved by those responsible for maintaining ventilation systems in buildings. The standard also recognises that different building and room uses require different standards.
The existing guidance document for ventilation systems in Health Estates is Health Technical Memorandum (HTM) 03-01: Specialised ventilation for healthcare premises. Part B addresses operational management and performance verification. HTM 03-01 was published in 2007, and has a strong focus on operational effectiveness, particularly for specialised and critical ventilation systems. All HTM’s are designed to complement the relevant European and international standards. BS EN 15780:2011 has been in force since April 2012, and consequently those responsible for maintenance of ventilation systems in Health Estates may not yet be fully up to speed on the requirements.
The main areas where the British Standard varies from the HTM relate to:
The HTM has some very clear principles with relation to the effective and safe operation of ventilation systems. These are that:
Clearly the scope of the HTM covers far more than the cleanliness requirement of the ventilation systems, but equally the cleanliness can and often does have a significant impact on the effective and safe operation of the systems.
There are, however a number of very specific requirement of the HTM in respect of system cleanliness. These are:
General requirements
1. The plant must not contain any material or substance that could support the growth of microorganisms.
2. The plant must not contain any material or substance that could cause or support combustion.
The document then gives more specific detail on ventilation system cleaning, and states that:
Ventilation system cleaning
The intake section of a ventilation system should be vacuumed-out as necessary to remove visible particles.
It can be seen from the HTM that while there are very specific requirements around inspection and cleaning of ventilation equipment there are no definitive criteria for cleanliness standards, or guidance on appropriate cleanliness standards for systems with different building uses or applications. These are the areas where the British Standard does provide more detailed and explicit direction.
BS EN 15780:2011applies a four stage approach to system cleanliness.
1. Assessment of the need for cleaning
The key instrument for assessing the need for cleaning is the inspection plan, which should include:A review plan and reports, including cleanliness quality class and measurement methods;
Quality Classes
The quality classes for building and room usage are defined below. For health facilities it can be seen that the lowest classification is medium for general areas. Any treatment areas are classified as High.
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, sport buildings, general areas in hospitals and general working areas in industries.
HIGH Laboratories, treatment areas in hospitals, high quality offices.
Once the quality class has been defined, the recommended inspection intervals follow. It can be seen from this that the British Standard recommends that filters and humidifiers in ventilation systems within treatment areas and laboratories etc. are inspected at 6 month intervals, compared with the annual recommendation in the HTM.
Recommended inspection intervals according to cleanliness quality class, in months:
AHU Filters Humidifiers Ducts Terminals
Low 24 12 12 48 48
Medium 12 12 6 24 24
High 12 6 6 12 12
2. Cleaning plan
If, following assessment, cleaning is needed the standard defines the need for a cleaning plan, which should include details such as:
3. Cleaning methods
The standard is not specific on cleaning methods, but states that they shall be sufficient to achieve the required level of cleanliness without damage to the system, to building users’ health and safety, and to the environment generally. Experienced air hygiene contractors will be familiar with the most appropriate method to use for different system designs and layouts, and further guidance is also given in the Building and Engineering Services Association (formerly HVCA) code of practice document TR19.
4. Evaluation and reporting
Evaluation of cleaning:
The standard states that final evaluation of cleaning should be made after the system has first been assessed as visually clean. It further states that objective verification of post-clean cleanliness should be carried out where necessary or as a result of any dispute or uncertainty.
Acceptable cleanliness levels
Supply ductwork Recirculation or secondary air ductwork
Low risk < 4,5 g/m2 < 6,0 g/m2
Medium risk < 3,0 g/m2 < 4,5 g/m2
High risk < 0,6 g/m2 < 3,0 g/m2
Measurement:
The preferred measurement method defined in the British Standard is derived from the Finnish vacuum test method whereby a gravimetric result is achieved. This method is suitable for circular, flat-oval and rectangular sheet metal duct types.
This method is not suitable for internally-lined (or other irregular, porous surface) ductwork, in which case the gel tape method is preferred. Since no standard limit values have been defined using this method, voluntary agreements will need to be made on a case by case basis.
Unacceptable fouling – Extract
For dry dust-affected extract ductwork (where the air is discharged to atmosphere) less stringent limit values are applied. Extract systems should be cleaned when airflow through the system reduces by 15 % or more.
Cleaning report
The British Standard recommends that a post clean report shall be prepared. It is very specific about the detail required within the report, which should cover information nf the building and ventilation system, dates of cleaning, methods used and assessment before and after cleaning.
Conclusions
The introduction of the new Standard should be seen as a positive development for Health Estates professionals. HTM 03-01 provides solid and appropriate guidance designed very specifically for the particular requirements of ventilation systems in Health Estates. BS EN 15780 complements this by providing clear definitions to enable facilities staff to:
- assess the need for cleaning
- assess the frequency cleaning is required
- decide what method of cleaning to adopt, and
- measure objectively the effectiveness of cleaning and adjust their regime as necessary.
By using BS EN 15780 alongside HTM 03-01 those responsible for managing the safe and efficient operation of Healthcare Estates can be sure they are applying best practice for air quality, health and safety and minimising the risk of spreading airborne contaminants and bacteria.
It is worth noting that the standard stresses the need for the inspection plan to describe the requirements of the specific qualification and experience for inspectors before they are authorised to carry out inspection work.
Quality Classes
The quality classes for building and room usage is defined in the table below. For health facilities it can be seen that the lowest classification is medium for general areas. Any treatment areas are classified as High.
One the quality class has been defined, the recommended inspection intervals follow. It can be seen from this that the British Standard recommends that filters and humidifiers in ventilation systems within treatment areas and laboratories etc. are inspected at 6 month intervals, compared with the annual recommendation in the HTM.
by Andrew Steel, Managing Director, Airmec
This article was first published in The HefmA Pulse, Vol 20, October 2013
http://www.hefma.co.uk/the-hefma-pulse
The introduction of a new British Standard for cleanliness levels in ductwork has a number of significant implications for Health Estate professionals. BS EN 15780:2011 Ventilation for buildings – Ductwork – Cleanliness of ventilation systems clearly defines vital goals to be achieved by those responsible for maintaining ventilation systems in buildings. The standard also recognises that different building and room uses require different standards.
The existing guidance document for ventilation systems in Health Estates is Health Technical Memorandum (HTM) 03-01: Specialised ventilation for healthcare premises. Part B addresses operational management and performance verification. HTM 03-01 was published in 2007, and has a strong focus on operational effectiveness, particularly for specialised and critical ventilation systems. All HTM’s are designed to complement the relevant European and international standards. BS EN 15780:2011 has been in force since April 2012, and consequently those responsible for maintenance of ventilation systems in Health Estates may not yet be fully up to speed on the requirements.
The main areas where the British Standard varies from the HTM relate to:
- Methods for classification of cleanliness quality;
- Definition of how to assess the need for cleaning
- Assessment and guidance on frequency of system inspections
- Selection of cleaning methods
- Guidance on how to assess the result of cleaning.
The HTM has some very clear principles with relation to the effective and safe operation of ventilation systems. These are that:
- All ventilation plant should meet a minimum requirement in terms of the control of Legionella and safe access for inspection and maintenance.
- All ventilation plant should be inspected annually.
- The performance of all critical ventilation systems (such as those servicing operating suites) should be verified annually.
- Compliance with the quality assurance requirements of items processed in pharmacies and sterile services departments is achieved.
- Staff, patients and the public are protected from harmful organisms and toxic substances.
Clearly the scope of the HTM covers far more than the cleanliness requirement of the ventilation systems, but equally the cleanliness can and often does have a significant impact on the effective and safe operation of the systems.
There are, however a number of very specific requirement of the HTM in respect of system cleanliness. These are:
General requirements
1. The plant must not contain any material or substance that could support the growth of microorganisms.
2. The plant must not contain any material or substance that could cause or support combustion.
The document then gives more specific detail on ventilation system cleaning, and states that:
Ventilation system cleaning
The intake section of a ventilation system should be vacuumed-out as necessary to remove visible particles.
- Air Handling Units (AHUs) should be vacuumed-out and/or washed down internally as necessary to remove obvious dust and dirt.
- Chiller batteries, humidifier units, energy-recovery batteries or plates and their drainage systems should be washed down with hot water annually to remove visible contamination.
- Filtered supply air distribution ductwork will require internal cleaning only when it becomes contaminated with visible dirt.
- Unfiltered extract air systems should be cleaned as frequently as necessary in order to maintain their operating efficiency. Room extract terminals, particularly those sited at low level in critical care areas, will need regular cleaning.
It can be seen from the HTM that while there are very specific requirements around inspection and cleaning of ventilation equipment there are no definitive criteria for cleanliness standards, or guidance on appropriate cleanliness standards for systems with different building uses or applications. These are the areas where the British Standard does provide more detailed and explicit direction.
BS EN 15780:2011applies a four stage approach to system cleanliness.
1. Assessment of the need for cleaning
The key instrument for assessing the need for cleaning is the inspection plan, which should include:A review plan and reports, including cleanliness quality class and measurement methods;
- determining which systems will be inspected
- determining where to inspect and sample
- choosing appropriate equipment and tools
- The assessment frequency
Quality Classes
The quality classes for building and room usage are defined below. For health facilities it can be seen that the lowest classification is medium for general areas. Any treatment areas are classified as High.
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, sport buildings, general areas in hospitals and general working areas in industries.
HIGH Laboratories, treatment areas in hospitals, high quality offices.
Once the quality class has been defined, the recommended inspection intervals follow. It can be seen from this that the British Standard recommends that filters and humidifiers in ventilation systems within treatment areas and laboratories etc. are inspected at 6 month intervals, compared with the annual recommendation in the HTM.
Recommended inspection intervals according to cleanliness quality class, in months:
AHU Filters Humidifiers Ducts Terminals
Low 24 12 12 48 48
Medium 12 12 6 24 24
High 12 6 6 12 12
2. Cleaning plan
If, following assessment, cleaning is needed the standard defines the need for a cleaning plan, which should include details such as:
- a summary of the assessment including the list of the systems and parts that need to be cleaned;
- cleaning methods to be applied;
- protection of the rooms in which the cleaning equipment is used;
- microbiological considerations when relevant, including considerations for the use of disinfection.
3. Cleaning methods
The standard is not specific on cleaning methods, but states that they shall be sufficient to achieve the required level of cleanliness without damage to the system, to building users’ health and safety, and to the environment generally. Experienced air hygiene contractors will be familiar with the most appropriate method to use for different system designs and layouts, and further guidance is also given in the Building and Engineering Services Association (formerly HVCA) code of practice document TR19.
4. Evaluation and reporting
Evaluation of cleaning:
The standard states that final evaluation of cleaning should be made after the system has first been assessed as visually clean. It further states that objective verification of post-clean cleanliness should be carried out where necessary or as a result of any dispute or uncertainty.
Acceptable cleanliness levels
Supply ductwork Recirculation or secondary air ductwork
Low risk < 4,5 g/m2 < 6,0 g/m2
Medium risk < 3,0 g/m2 < 4,5 g/m2
High risk < 0,6 g/m2 < 3,0 g/m2
Measurement:
The preferred measurement method defined in the British Standard is derived from the Finnish vacuum test method whereby a gravimetric result is achieved. This method is suitable for circular, flat-oval and rectangular sheet metal duct types.
This method is not suitable for internally-lined (or other irregular, porous surface) ductwork, in which case the gel tape method is preferred. Since no standard limit values have been defined using this method, voluntary agreements will need to be made on a case by case basis.
Unacceptable fouling – Extract
For dry dust-affected extract ductwork (where the air is discharged to atmosphere) less stringent limit values are applied. Extract systems should be cleaned when airflow through the system reduces by 15 % or more.
Cleaning report
The British Standard recommends that a post clean report shall be prepared. It is very specific about the detail required within the report, which should cover information nf the building and ventilation system, dates of cleaning, methods used and assessment before and after cleaning.
Conclusions
The introduction of the new Standard should be seen as a positive development for Health Estates professionals. HTM 03-01 provides solid and appropriate guidance designed very specifically for the particular requirements of ventilation systems in Health Estates. BS EN 15780 complements this by providing clear definitions to enable facilities staff to:
- assess the need for cleaning
- assess the frequency cleaning is required
- decide what method of cleaning to adopt, and
- measure objectively the effectiveness of cleaning and adjust their regime as necessary.
By using BS EN 15780 alongside HTM 03-01 those responsible for managing the safe and efficient operation of Healthcare Estates can be sure they are applying best practice for air quality, health and safety and minimising the risk of spreading airborne contaminants and bacteria.
It is worth noting that the standard stresses the need for the inspection plan to describe the requirements of the specific qualification and experience for inspectors before they are authorised to carry out inspection work.
Quality Classes
The quality classes for building and room usage is defined in the table below. For health facilities it can be seen that the lowest classification is medium for general areas. Any treatment areas are classified as High.
One the quality class has been defined, the recommended inspection intervals follow. It can be seen from this that the British Standard recommends that filters and humidifiers in ventilation systems within treatment areas and laboratories etc. are inspected at 6 month intervals, compared with the annual recommendation in the HTM.