FEATURE ARTICLES
AIR FILTRATION CASE STUDY By Simon Young AES Environmental
A large hospital in regional NSW engaged a contractor in 2017 for the NATA validation and testing of its HEPA filters after the recent construction was completed. This regional hospital uses most of its operating theatres every day from 08:00 to 18:30 and then up to two theatres will remain in-use until 22:00 and remain on-standby for emergency. These operating theatres obtained passing results for several years but due to the recent bushfires in NSW it was determined that the performance of these theatres would be subjected to further investigation. The management of the Hospital had recently become incumbent to the maintenance of the operating theatres, this recent change exposed some remarkable aspects with regards to the previous maintenance and performance of the operating theatres.
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ES Environmental was commissioned by the new management to conduct the annual accreditation services in 2020. It was while conducting those services that problems were identified within the theatres concerning room pressures and HEPA filter air flows. A serious disconnect existed between the HEPA testing, Theatre Room Qualification and the facilities BMS operation. The BMS was lacing in credible, factual operational information for the management to make qualified decisions. Information that, in days past, would have been identified and forthcoming by qualified technicians working around the various plant and equipment. BMS however replaced much of these human assets within maintenance and with increasing reliance on BMS the input information becomes critical to correct operation. AES Environmental HEPA accreditation and reporting identified fundamental anomalies between what was reported within the BMS and actual room operation performance. It became remarkable as news of the AES Environmental accreditation information was slowly released within the hospital establishment; doctors, nurses, surgeons, admin, all expressed an interest. The user groups knew that something wasn’t quite right but under the “guise” of compliance. The HEPA filters had not been considered an issue for concern.
Investigation and Identification On initial assessment AES Environmental discovered several areas where significant improvements to theatre performance could be obtained. These were: • Leakage was identified during Integrity Testing (AS 1807.6) from some of the HEPA sealing arrangements. Leakage can be an indication that foreign particles can by-pass the HEPA filters and could result in a source of contamination in the operating theatre. • HEPA face velocities varied when measured at the entry. The fluctuations were between 0.4m/s at the lower level and 1.05m/s at the higher level. This is significant variation from HEPA filters that are only three years old and could be an indication of poor air flow characteristics, excessive dust loading or set-up issue. • Theatre room pressures remained inconsistent and in some operating theatres what should have been a positive pressure to the immediate next room was actually recording a negative pressure of air in to the room. • Individual HEPA pressure readings were inconsistent with some registering very high levels while others were minimal pressures. This is consistent with the variation in the HEPA face velocities. • Annual testing was being conducted however this was not in conjunction with visits from the BMS supplier
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