A fieldwork measurement and simulation studies were carried out at the operating room (OR)-5, Sarawak General Hospital Heart Centre (SGHHC). This hospital is located in East Malaysia and was commissioned in January 2011. The air condition at the inlets and several other locations in the room are measured for the validation of the computational fluid dynamics simulation. From the results, it is noted that the obstruction and heat dissipation effects from the surgical light should not be disregarded. The combination of both effects results in trapped heat in the region below the surgical light. Under the same total flow volume for the OR, it is observed that the OR with the uneven inlet velocities performs better than the OR with an even velocity distribution at the inlets. On the question of reducing the ventilation air consumption, it is proven that a reduction of air flow rate by 15% (to the average inlet air velocity of 0.3 m/s) is possible in the OR.

A practical case study on the air distribution in an operating room (OR) at University of Malaya Medical Centre, Kuala Lumpur is presented. The OR has a relatively large floor area since it is connected with the medical storage room and served by a total of 14 room air inlets and 3 exhausts. The room air inlets are located at the peripheral of the surgical site rather than just above the surgical site. From the measurement conducted, the average room inlet air velocity was 0.19 m/s with a standard deviation of 0.03 m/s for all inlets and 33.5 air change per hour. In line with its current design, the air distribution was simulated using the computational fluid dynamics software. Initial simulation with the room air inlet velocity of 0.2 m/s showed an improper airflow at the surgical site. However, this condition was not significantly improved even by doubling the inlet velocity. The results have identified that with air inlets located at the peripheral of surgical site, the air inlet design was unable to provide a satisfactory airflow across the surgical site, and hence not appropriate for the purpose of its intended use.

In this paper, a room with four inlets located at the ceiling in the centre of the room with an exhaust installed at the bottom sidewall was modelled and investigated. The air is supplied through the individual room air inlets filtered by a high-efficiency particulate air filter, and the air is removed from the room via the exhaust located at the bottom sidewall. It leads to two possible inlet arrangements with four inlets: 1 × 4 array and 2 × 2 array. In the modelling, an obstacle is built to represent a workbench located underneath the inlets. Both the array designs are compared on their air flow and ability to remove gaseous contaminants. This study also suggests that the behaviour of the air jet impingement on the surface of the obstacle must also be considered in determining the design of the inlet array in a clean room. Practical application: This paper is intended to provide a practical guide to building service engineers on the design arrangement of inlets for a Class 7 clean room. By using the same concept, the design arrangement concept can be extended to the sizing of a workbench (i.e. the obstacle) when there is a fixed inlet design.

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