Ventilation Requirements Paul Wilkings C.Eng. MIMechE. FIHEEM. Principal Engineer(Mechanical)
Documentation Ventilation in Healthcare Premises Health Technical Memorandum 2025 Design considerations Management policy Operational management Validation and verification
Documentation HTM 2025 will shortly be replaced by HTM03 Ventilation Systems. According to the DOH, this document is now expected to go to the publishers in the next few weeks and be available before the end of 2007. **It is important that all HTM s HBN s etc. are accessed from the WHE website, (www.wales.nhs.uk/whe) as there could be changes within the Welsh Document from the standard DOH document.**
Definitions Ventilation Ventilation is a means of removing and replacing the air in a space. In its simplest form this may be achieved by opening windows and doors. Mechanical ventilation systems provide a more controllable method. Basic systems consist of a fan and a collection of distribution ductwork; more complex systems may include the ability to heat and filter the air passing through them. Ventilating equipment may be required in order to remove smells, dilute contaminants and ensure that a supply of fresh air enters a space. Air-conditioning Air-conditioning is the ability to heat, cool, humidify, dehumidify and filter air. This means that the climate within a space being supplied by an air conditioning plant can be maintained at a specific level regardless of changes in the outside air conditions or the activities within the space. Air-conditioning equipment may be required in order to provide comfort conditions within a space.
Ventilation Requirements The following departments will usually have specialist ventilation requirements, either for a single room or throughout a suite: a. an operating suite; b. a laser surgery unit; c. an intensive treatment unit; d. an infectious diseases isolation unit; e. a manufacturing pharmacy and cytotoxic drug units; f. a specialist X-ray and scanning unit; g. pathology; h. a mortuary and dissection suites; j. research laboratories and associated animal houses; k. sterilizing and disinfecting unit (SDU).
Ventilation Requirements of an SSD Health Building Note 13 Sterile Services Department, requires the following :- The Inspection and Packing Room (IAP Room) is a Class 8 clean-room as defined in BS EN ISO 14644. It should have a nominal 20 air changes per hour with a positive pressure differential of not less than 10 Pa between it and adjoining rooms. The Changing Room, should have a positive pressure differential of not less than 10Pa between it and the adjoining corridor. This equates to the IAP Room being at least 20Pa higher than the corridor, as access to the IAP Room is through the Changing Room.
Problems and Consequences Ventilation plant itself has not been shown to pose a high risk to health, but it does have the ability to transfer a hazard, originating from another source, to a large number of people, without them becoming immediately aware of it. Ventilation systems that can be shown to be inappropriate, inadequate or ineffective and that give rise to proven failures can result in a civil suit by the patient against the operators, or even prosecution by a Government body. (Barrow in Furness outbreak in 2002. The prosecution of Barrow-in-Furness Council and Gillian Beckingham. Seven people died and hundreds of others were infected by a legionella outbreak that resulted from the cancellation of a contract to ensure that necessary tests were carried out on an air conditioning unit.)
Responsibilities Management has a general responsibility to ensure that ventilation systems are operated at a standard suitable for the purpose for which they were installed. When new ventilation systems are accepted for use, full information, proving the designed mode of operation has been achieved, together with recommended maintenance procedures should be provided as part of the handover procedure.
Air Handling Unit plant room showing debris and water ponding on plant room floor. Any stagnant water is a breeding ground for legionella etc.
Instrument traceability equipment showing buildup of dirt and dust.
Build-up of flies inside Air Handling Unit
Incorrect choice of AHU equipment. Finned frost coil fitted instead of tubular type. Because pre filter is downstream of this coil fins have blocked up with dirt, debris and insects. Blocked coils reduce air flow to the spaces served, the result is that the air pressure regime is lost and hence the invisible barriers to infection are also lost.
Example of what can happen when things go really wrong! Photo shows a bird s nest inside an Air Handling Unit. This AHU was supplying an opthalmic theatre. It was shut down immediately, when we showed the Theatre Manager.
WHE recently undertook a survey of all the Operating Theatres in Wales, a few of the results showed the following;
Summary In conclusion there is a need to be aware of the ventilation/air conditioning requirements of individual departments they are not all the same. Air flows and pressure regimes for individual departments are extremely important, they set the invisible barriers to infection and are the first line of containment. Be aware of all new documentation; but access all documents from the WHE website, as there could be differences appertaining to the Welsh versions from the standard DOH documents. (www.wales.nhs.uk/whe)
One of the UK wide changes that we know is going to happen, is that split cassette type air conditioners and fan coil units are not going to be recommended for use in critical areas, such as ITU s, Cardiac Units, Renal Units etc. due to the high risk of infection that is associated with them. There have been a lot of these incorporated in recent designs. These may prove to be a problem in the future. While it is true that Trust Management is responsible for the correct day to day operation of equipment, it is also true that key project personnel such as project managers, planners, designers, contractors etc. are responsible for providing them with buildings and departments that are compliant to current documentation and legislation and proven to be fit for purpose, prior to occupation.
Thank You