Heating and Ventilating

Healthcare facilities are at particular risk from airborne infections transmitted via poorly maintained ventilation and air conditioning systems, says Alan Gregory
Many facilities managers are playing a dangerous game with patients' health by ignoring the threat posed by airborne contaminants in healthcare facilities. The fact that the source of the infections is 'out of sight out of mind' should not be an excuse for overlooking ventilation systems when planning preventative maintenance regimes.

One clear, and rather shocking example, is that less than 5% of air conditioning systems have been inspected even though this is a mandatory requirement under the European Energy Performance of Buildings Directive (EPBD).

A large body of research has established a clear link between poorly maintained ventilation ductwork and the spread of airborne infections. Vulnerable patients, whose immunity is already reduced, are being put at particular risk.

Vigilance against the threat of cross-contamination is even more urgent these days since buildings have been made more airtight to comply with the energy efficiency requirements of Part L of the Building Regulations. Rising temperatures and increased relative humidity (RH) make ideal breeding grounds for bacterial spores that can be distributed around wards and other occupied areas through the ventilation and air conditioning systems.

The dreaded MRSA, in particular, thrives in hot, stuffy environments between 18 and 37 deg C - hospitals are usually kept at around 24 deg C with relatively high humidity. The risks are particularly high in accident and emergency facilities and bone marrow transplant areas.

Bacterial spores in ductwork can often be behind outbreaks of MRSA and other serious infections in hospitals and clinics. 'The healthcare environment is a reservoir for potentially infective agents, which can spread unpredictably in ventilation and air conditioning systems making the risk difficult to control and manage,' healthcare expert Dr Ghasson Shabha told a Building & Engineering Services Association (B&ES) seminar recently.

'There is a plethora of empirical evidence to suggest that increasing air tightness will lead to health problems,' added Dr Shabha, who is senior lecturer at Birmingham School of the Built Environment. 'The indoor air quality of hospitals is becoming increasingly hazardous because of outdated mechanical ventilation and air conditioning systems.'

He also said that his research showed that the risk of cross-infection to patients through the extract and the supply system 'is significantly greater than patient-to-patient transfer'.

The ventilation hygiene industry is eager to address this potentially fatal problem, but the whole issue of cross-contamination is poorly understood by the healthcare sector - there is also a damaging lack of information to help NHS trusts make informed decisions. However, a combination of good practice, common sense and not avoiding the issue can help building operators avoid the very worst consequences. It is never too late to implement a cleaning regime.

Indequate maintenance regimes and protocols mean air extract and supply grilles, ductwork, air handling units (AHUs), extract fans and discharge points are becoming more prone to contamination that increases the risk for patients and other building users.

The B&ES Guide to Good Practice (TR/19) 'Internal Cleanliness of Ventilation Systems' provides details of how to measure dust accumulation and make systems safe for use. An ongoing programme of routine independent inspection should then be carried out in accordance with the Health Technical Memorandum (HTM 03-01) to maintain the systems at a safe level.

Grabbing the headlines
Remedial action always grabs the headlines, but getting things right in the first place is a much better strategy. B&ES recommends that users ensure their ductwork is clean before the facility is used for the first time. Ventilation hygiene firms, when eventually called in to sort out poorly performing systems, regularly encounter contaminants that have been in the system since it was first switched on. This can even include builders' rubble, which began clogging the filters before the occupants even moved in.

Having ductwork cleaned at pre-commissioning stage may push the cost of a ventilation installation project up by 5 or 10%, but that is money well spent. Not only will a modest upfront investment in cleaning improve the health of end users, much of it will be recouped over time by reduced on-going maintenance and energy costs. Properly cleaned ventilation costs considerably less to run than poorly maintained systems.

A fan left chugging round for years carrying the extra weight of dirt built up on its surface will use significantly more energy than if it was operating in a clean environment where the resistance is much lower. Components will also last longer because of reduced wear and tear on bearings.

Key items to concentrate on because they are prone to rapid buildup of deposits are: Air intake duct/plenums; air handling units/plant; heat transfer coils - particularly wet coils; humidifiers and surrounds; fan coil units; fire dampers; internal insulation; floor/ceiling plenums; induction units; and filters.

Items a contractor needs to implement a full hygiene maintenance strategy include:
· Schedule of all plant associated with the ventilation systems
· Ductwork layout drawings
· Component performance schedules (fan pressures, diffusers characteristics, filter pressure drops etc)
· Location of access doors

Whether at pre-commissioning or once the building is in use, separate thought should be given to the maintainability of the systems through their operating life.
There are also some key areas to consider when setting about eliminating health threats.

The cooling coil can be a major source of biological contamination. As air passes across the coil, water condenses onto the coil's surface and is collected underneath. Most of the particulates that escaped the filter are washed out, including organic debris, creating ideal breeding conditions for bacteria, mould and algae. Under such favourable conditions, these microbes multiply rapidly and moving air then circulates microbes throughout the system and into occupied spaces together with their reproductive spores and any toxins they produce.

Sorting out hygiene problems also does not necessarily require a complete shutdown of the facility. Ductwork cleaning can be done zone-by-zone or by 'capping off' sections or by working at night - so keeping most of the facility operational.

Many of the ventilation hygiene principles discussed here are little more than common sense and would apply to most buildings, but they take on even greater significance when the problems are found in facilities dedicated to keeping vulnerable people healthy.

// The author is chairman of the Ventilation Hygiene group branch of the Building & Engineering Services Association //