AIR CONDITIONING # It is also worth considering that healthcare buildings are a place of work and so the air conditioning systems also need to comply with the Health and Safety at Work Act 1974. The Act places a duty on an employer to maintain plants and systems so that they are, as far as is reasonably practicable, safe and without risks to workers’ health. THE TRACE OF BACTERIA When talking about bacteria in air conditioning systems, it is important to remember that all air conditioning systems will contain traces of bacteria and other organisms. In a well-maintained system the levels of bacteria are likely to be so low that healthy people are, generally, unlikely to be affected. However, in a healthcare building, where there are potentially many vulnerable people, some with compromised immune systems, the issue of bacteria in air conditioning systems can be much more serious. There are many forms of bacteria that can be found in an air conditioning system including MRSA, C. Difficile and Legionella, along with Aspergillus spores in the air itself. In healthy people its spores do not normally cause any harm. However, in a hospital setting with immunocompromised patients, Aspergillus can result in serious diseases including: invasive aspergillosis, allergic bronchopulmonary aspergillosis, chronic pulmonary aspergillosis and aspergilloma. To minimise the risk of Aspergillus spores, it is particularly important when considering the design or refurbishment of an air conditioning system not to locate the air intakes in the vicinity of compost heaps or any areas where decaying vegetation is present. Legionella is a bacterium which thrives in warm water in dark and dirty conditions, so it is important to ensure that no pools of water are present within an air conditioning system. Generally the occurrence of water will be due to poor system design rather than any shortfall in the maintenance and ductwork cleaning regimes. Split air conditioning units or comfort cooling units can be particularly susceptible to Legionella. These units are allowed by HTM 03-01, but only for non-critical areas. In reality they should be limited to office type accommodation or seminar rooms because split units produce condensate. There can be an issue with these units when small quantities of condensate are produced, which can lead to pooling and puddling of water which can then become stagnant and can increase the possibility of legionella developing. To avoid this, the condensate drains from the
split air-conditioning units should comply with the requirements of HTM 03-01. INSPECTION AND INSTALLATION HTM 03-01 Part B requires all ventilation systems to be subject to at least one visual inspection annually. In the case of critical care ventilation, these systems should be inspected quarterly with their performance measured and verified on an annual basis. Air conditioning systems should be designed as a series of smaller systems specific to a department or area rather than one giant system so that they can be easily managed. In the case of operating theatres, for example, one air conditioning system should be dedicated to each theatre. This will contain any bacteria and reduce the need to close more than one theatre when maintenance is required. Outside air intakes to the air conditioning system must be located in a suitable position and kept clean. The Chartered Institution of Building Services Engineers’ (CIBSE) document TM21 Minimising Pollution at Air Intakes provides designers with the information that will help in locating ventilation inlets. Air exhausts should be a minimum distance of 4m from an air intake and, ideally, 10m apart to stop the exhausted air recirculating into the supply air intake. Air conditioning systems incorporate filters to remove particulates from the air.
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general areas in hospitals; and high, such as laboratories, treatment areas in hospitals and high quality offices. The standard also recommends a system assessment frequency. The standard states that an inspection frequency should be specified and not a cleaning frequency to allow for changing conditions that may actually alter the frequency at which a system needs to be cleaned. Providing correct filtration to the appropriate standard and class for the area served will reduce the possibility of bacteria in the air conditioning system. Filters should be inspected and maintained in accordance with the recommendations of the manufacturers taking into account the location of the hospital and the air intakes. For hospital environments, it is recommended that air handling units (AHUs), ductwork and air terminals be inspected annually, in line with HTM 03-01 for annual inspection and verification of ventilation systems.
Facilities Management
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CLEANLINESS QUALITY CLASS In order to reduce the build-up of bacteria in the ventilation system the appropriate ductwork cleaning is required before the system is brought in to use and while the system is in use. Dust can also carry the spores of Aspergillus, so cleaning new installations to reduce the presence of dust is vital at both the installation and commissioning stages of an air conditioning installation. In addition to providing a safe and clean system, ensuing that ductwork is clean from new helps reduce energy use. Apart from obvious clinical benefits it makes
The primary role of ventilation in a healthcare environment is to dilute and control airborne pathogens, provide thermal comfort and supply fresh air to occupants, and, therefore, air conditioning systems can take many forms If the correct filters are used and these are correctly installed then it should not be necessary to clean ductwork on an annual basis. If ductwork is dirty, that would usually signify that the filters are not working correctly or that the filtration is inadequate or has not been properly maintained. Correctly installed filters should keep ductwork clean for up to 10 years. The British Standard, BS EN 15780:2011 categorises the level of cleanliness in ductwork into the three quality classes: low, such as rooms with only intermittent occupancy e.g. storage rooms and technical rooms; medium, such as offices, schools restaurants and
good business sense. Keeping air conditioning systems bacteria free (or as bacteria free as possible) is down to good design, installation and maintenance. In a well-designed system, ductwork cleaning should only be considered where the annual inspection has highlighted a need. Finally, it is worth considering that bacterial contamination in healthcare facilities is far more likely to come from the people in that environment than from a well-designed and maintained air conditioning system. ! FURTHER INFORMATION www.cibse.org
Volume 18.1 | HEALTH BUSINESS MAGAZINE
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