Service and Verification of Critical Systems, including Common Failures in Healthcare

Concerning critical healthcare ventilation systems, NHS England has provided a specific document outlining requirements – HTM 03-01 (2021), Part B. We also cross reference other documents for annual assessment, such as Control of Substances Hazardous to Health 2002, HSG 258, BESA TR40, and many different pieces of guidance and legislation.

Concerning legislation, LEV systems?MUST?be assessed (every 14 months unless the process changes or it is outlined in Schedule 4 of COSHH 2002, but this is unusual in Healthcare), and?critical HVAC systems MUST be annually assessed in line with HTM 03-01 (2021), Part B. HTM 03 is also referenced in Part F (Volume 2) of the Building Regulations 2010.

In my experience, Healthcare establishments list “critical” spaces in a different fashion. As the building is a hospital, some sites define “critical” as every single AHU within the building. Others define “critical” as AHUs that directly impact patient safety. It is the responsibility of the Ventilation Safety Group (VSG) and the AE(V) to define this scope to the appointed, competent sub-contractor, along with the scope of works.

Critical Ventilation – The AHU (Air Handling Unit)

The AHU could be argued to be the most important part of a critical ventilation system. Although “out of sight” it is a mechanical piece of equipment that should be carefully maintained, assessed, significantly serviced at the tenth anniversary, and completely replaced at the twentieth (as per HTM 03-01 (2021), Part B, Section 1.51 and the CIBSE guide for maintenance (Guide M)).

All too frequently we see AHUs that are poorly maintained, and on some occasions not even annually verified when captured in new contracts or serviced by other third-party companies. Key components of the AHU should be annually assessed by an adequately competent person and quarterly inspected by the onsite engineers, who should be as equally competent (as per the requirements of HTM 00).

Figure one gives an example of some of the AHUs that we come across in the UK. Clear neglect of basic AHU servicing will almost certainly increase the risk to patients and reduce the lifespan of the equipment – increasing costs in the long run.

The HVAC system must have a robust maintenance schedule along with unique referencing, up-to-date logbooks, and spare storage of filters, fans, and any other component deemed a requirement in the equipment Operations and Maintenance manuals.

For information on storage and basic considerations around the AHU please read through Chapter 3 (Minimum Standards) in HTM 03-01 (2021) Part B, which is coincidently included in all Initial VALIDATIONS (on new systems) completed by our technical team, with the philosophy being if this is achieved at install it will be achieved for the expected lifespan of the equipment/installation.

Critical ventilation – The AHU (Microbiological Risk)

A key component of the AHU is to heat and cool large volumes of air delivered to the critical spaces. An appreciation of microbiological risk should be considered by the hospital engineer and the AHUs have features on them that should be cross-checked at quarterly inspections (over and above basic checks of filtration pressure drops, visual 3 port inspections, belt and pulley tensions, etc.).

Glass traps, drainage trays, excessive corrosion, failed attenuation, gaps under cooling coils, drift eliminators (where face velocity exceeds 2 m/s), Humidification control (in specialist environments,) and any other specifically outlined AHU component in the O&M or subject to specific Risk Assessment by the VSG MUST be checked and considered.

Some basic examples of this are found in the next section.

Borosilicate Glass Traps.

Inspection traps should be clear, filled with water, and be of the correct orientation on the AHU drainage system. The reason this is clear is so that an assessment of the water colour can be made as per the table below.

Figure 2 gives an example of a drift eliminator installed downstream of a cooling coil showing signs of microbiological growth.

This is also an example of poor maintenance and, in this instance, poor management of sub-contracted resources employed to clean the critical AHUs on this particular site. HTM 00 specifically places the responsibility on the hospital to ensure that sub-contracted resources are competent – this is another failure in line with the specific TMs.

Almost certainly there would have been failures in the clinical areas if microbiological sampling (MBAS) had been undertaken in the conventional operating theatre attached to the other end of this system.

Figures 3 and 4 below also offer some insight into AHUs that have been inspected (and subsequently failed). All components of the AHU must be assessed and in HTM 03 01 (2021) Part B, a full in-depth checklist is given for the AHU in Appendix 1.

The assessment asks the verifying engineer to analyse the general condition of the AHU (End of useful life, Poor, Average, Good) and then compliance with minimum healthcare standards (Poor, Average, or Good). Each time an engineer assesses the mechanical system it is done so with a clean slate and the questions are simply answered. Part B is written in a fashion where opinion is removed and the evidence is photographed and factual – a concept that is on occasion challenged by hospital engineers.

As previously stated – the AHU is a significantly important part of the system, which ultimately is installed to protect the patient and provide an environment that promotes good control of infection/risk. Although out of sight it should be well designed, installed, maintained and most importantly continuously monitored (unlike Figures 3 & 4).

Understanding Air Change Rates

Of course, the verification visit to a critical system is not just a visual assessment of the AHU, there is also an assessment of many different areas (see the final image/conclusion of this article), however, one that is frequently assessed is the performance of the AHU and as a result – the clinical area air change rate.

I often discuss the air change rate with customers and the airflow into critical spaces. It is firstly important to note that the air delivered into the space is not solely there for the air change rate. The conditioned air delivered is also responsible for supporting the pressure regime, ensuring that door protection is appropriate, providing temperature, and achieving adequate humidity across the rooms under assessment.

In many verification reports an air change rate is noted (and then cross-checked back to the requirements of HTM 03-01), and an 80% rule may be applied within the document (where 80% of the air change rate is achieved against the design / HTM requirements). This then enables a RAG system to be applied. Over design is green, between 80 – 100% is amber and under 80% is red.

Air change rates may seem on some occasions hugely excessive – but this is there to ensure closed/open door protection in the rooms, and any alteration of air volume (around sustainability strategies) should be carefully considered.

An example of how air change rates are communicated can be found in Table 2 (below).

As you can see from the table above there are some constants (Room Volume / Requirements from HTM / Seconds in an hour – which is 3600) and there is a variable (The amount of air delivered in m3/s and then converted into m3/hr.). We can use this knowledge to execute EQ 1 & 2 below for an air change assessment.

Air Change Rate Calculation

As you can see EQ1 & 2 work together to achieve the calculated air change rate.

This calculation can be transposed for design – this is not covered in this article.

EQ1

Air Change Rate = Airflow (in m3/s) · 3600 = Airflow in (m3/hr)

EQ2

Air Change Rate = Airflow (in m3/hr) / Room Volume (in m3)

Electrical Compliance and Essential Switchgear

As standard ALL UCV Canopies have some form of switchgear that enables interfacing with the BMS system, Theatre Control Panels, and offers controls to the physical unit within the operating theatre. Alterations to regulation mean that on new installations these control panels should be local to the UCV operating theatre (on the same level), but it is not uncommon to find them located in the corner of a plant room.

Irrespective of the location, these panels should have local isolation, correct signage, a distribution schedule, be marked for area supplied, and have all relevant CE data fixed to the control panel.

Some third-party control equipment uses old variac type transformers and these can be susceptible to fire. Old terminals within panels should at least be checked annually in line with the verification. Running frequencies, running currents, and panel filter media should all be checked and replaced as per the scope of work to ensure the safe use of the equipment.

Electrical Engineering is an important discipline that is often overlooked at verification for a cheaper “read and record” approach. This in the long run costs more due to defective equipment and components exceeding expected life (putting the equipment unnecessarily at risk). Figures 5 and 6 are examples of poor electrical maintenance.

LEV Systems

LEV systems, particularly in healthcare can be overlooked, are often misunderstood, and are just as important as any other item or critical system within the trust.

A failure that has been noted in the past around Healthcare LEV Systems is that they are often managed by “Clinical” owners. Examples include: Class I and II Microbiological Safety Cabinets, Mortuary downdraft tables, Small LEV Systems found in dentistry or plastering departments, Cut up benches, Ventilated storage cabinets, and workshop wood saws.

Under normal circumstances, this ownership is not an issue. However, in Healthcare we have a team of microbiologists for example scheduling engineering works that should be managed by the AP(V) on site, as the engineer will need to be inducted and managed around various plant rooms and roof spaces as discharge stacks need to be inspected and isolations implemented in line with RAMS (Risk Assessment Method Statement) and SSoW (Safe Systems of Works).

HSG 258 outlines very specific information for LEV TExT (Thorough Examination and Test) and outlines the LEGAL requirements set out in COSHH 2002 Regulations. It is the responsibility of the employers to ensure that LEV systems are adequately designed and fit for purpose from the outset, and a frequent failure here is the purchasing of an “off the shelf” solution when in reality a full Risk Assessment by a suitably qualified and competent person is required (Usually Occupational Hygienist or Similar).

Engineering qualifications around LEV systems are also slightly different with the BOHS leading the way in this area and the CoC (Certificate of Control) being the highest level of qualification (and experience).

LEV in recent years has improved significantly within healthcare, but there is still some way to go managing the entire estates LEV system to an adequate level. Figure 7 offers an insight into issues only ever picked up on inspection.

(BESA TR40 / HSG 258 / COSHH 2002 – LEV System guidance)

The UCV Canopy – Service & Maintenance

UCV Systems must also be annually checked. UCV Systems have pre-filters in them, these should be replaced every 3 – 6 months. Howorth also recommends that the airflows be confirmed at this time too, however, this is not a statutory requirement.

All elements of the UCV Canopy should be checked. Some third-party UCV Canopies have in the past had gel seal filters installed and some still exist in the estate even though notice on these installations have been circulated in 2016. Howorth has NEVER installed gel seal filters within their UCV Canopies. See Figure 8 for signs that you have gel movement.

UCV systems also have Mechanical parts that require inspection. All Fans, doors, and hinges should be checked for wear. All pressure switches, digital inputs, lighting, and drives should be checked at the annual assessment as outlined by the scope of work. All of these checks, along with pre-filter replacement are standard practice for Howorth customers.

Service & Verification Conclusion – Your Obligation

For further information about service and verification, please contact me via InMail.

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