VENTILATION
Ventilation hygiene has building
classifications that clearly identify hospital ventilation as a high-quality area as shown in Table 1.
As highlighted in BS EN 15780:2011
there is already a recognised regime for inspection and maintenance in hospitals and it is clearly defined within NAAD-21 – see this in Table 2. Ventilation hygiene requirements in
these areas are clearly defined and show what is a compliant acceptable level of cleanliness within systems – see Table 3. It should be noted that from this chart
there are higher standards for HTM03, SHTM 0301, and WHTM 0301, i.e. hospitals on the frequency of cleaning ATD in general parts of hospitals every 12 months. In acute high-risk areas, every three months – see Table 4.
Who should be conducting the testing, inspection and cleaning? NAADUK has been collaborating with others within the sector to improve the standards of maintenance which resulted in the publication of NAAD21. With the collaboration of training instructors, auditors, and assessors, a full programme has been developed to create a certification to SVQ Level 5 GT0F 04 SCQF (NVQ2). It covers the practises and procedures of the BSEHV11, the National Occupational Standard for cleaning industrial and commercial ventilation systems. This qualification should be considered the minimum standard for ventilation hygiene technicians. All testing and cleaning in the hospital
environment should be conducted by competent qualified persons. The company that is completing the
works should have 3rd party accreditation. Section 10 of NAAD-21 highlights this
clearly.
How the testing should be completed? There are several recognised testing methods when it comes to ventilation hygiene levels – these are predominantly split into 2 categories: l Dust contamination. l Microbiological.
The NAADUK tests for these are as follows: l Vacuum testing (with the adapter). l Contact slides. l Agar plates.
There are also Deposit Thickness Tests. However, here at NAADUK we do not recommend anyone uses this method as it is typically not sensitive enough to be accurate on post clean. In light of the information above, NAADUK would recommend the Vacuum Test (VT) test to be used for dust sampling. When using the VT test,
IFHE DIGEST 2023
Table 1. Typical applications of cleanliness quality class. Quality Class Typical examples Low
Medium
Rooms with only intermittent occupancy e.g. storage rooms, technical rooms
Offices, hotels, restaurants, schools, theatres, residential buildings, sports buildings, general areas in hospitals and general working areas in industries
High
Laboratories, treatment areas in hospitals and high quality offices Taken from BS EN 15780:2011 – Table A.2
Table 2. Quick check guide as to frequency of inspection and testing. Low
Medium AHU Filters
Humidifiers Ductwork
Air Terminal Devices
24 months 12 months 12 months 48 months 48 months
12 months 12 months 6 months 24 months 24 months
High
12 months 6 months 6 months 12 months 12 months
Taken from BS EN 1S780:2011
NAADUK recommends pre-weighed filter cartridges, pre-barcoded to prevent mistakes or wrongly attributed figures, and we always recommend an independent laboratory to UKAS standards that provides full certification. All microbiological samples should be tested and at NAADUK we recommend an independent laboratory to UKAS standards that provides full certification. The parameters for microbiological
contamination can be found in CIBSE TM26 Table 3 – Classification of surface sampling microbial limits. All testing and inspections should
Table 3. Acceptable cleanliness levels. Cleanliness quality class
have the information recorded in a clear, concise, photographic report, incorporating laboratory analysis certificates and advisory notifications.
What should happen when a sample fails? Whenever a sample location is above parameters, this does not mean that the whole system requires cleaning. This is highlighted in CIBSE TM26 10.2.2 for microbiological sampling. With dust contamination, we have to look at the system criteria and being a qualified competent person make a
Acceptable cleanliness level Acceptable cleanliness level Supply ductwork
Recirculation or secondary air ductwork
Low
Medium High
<4.5 g/m2 <3.0 g/m2 <0.6 g/m2
<6.0 g/m2 <4.5 g/m2 <3.0 g/m2
Taken from BS EN 15780:2011 – Table A.3
Table 4. Acceptable dust accumulation levels in new ductwork. Cleanliness quality class
Acceptable dust accumulation level
Supply, recirculation or secondary air ductwork
Low
Medium High
<0.9 g/m2 <0.6 g/m2 <0.3 g/m2
Acceptable dust accumulation level Extract ductwork
<1.8 g/m2 <1.8 g/m2 <0.9 g/m2
Taken from BS EN 15780:2011 – Table A.4 57
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