CLEANROOM VENTILATION | COMMERCIAL OFFICES per hour, and the CO2-activated fan will double this at peak occupant demand with ventilation air. Comparative testing of solutions Figure 2: Mock-up boardroom for eight people, representing a high-risk environment for the transmission of viruses (extract system not shown) Elevated CO2 concentration corresponds very well with elevated human activity this was employed as a proxy for potential air contamination in these tests. This second unit remains idle until there is a demand for ventilation air that is triggered by rising CO2 levels the units fan speed modulates to manage the associated airborne risks presented by the human activity in the room. The first unit provides approximately 12 recirculation air changes To assess the efficacy of the boardroom system, a test based on cleanroom industry practices was devised to compare its performance against a commercially available mobile unit. The space was challenged with particulates at a concentration of more than 100,000 per m3. A particle counter took cumulative counts every minute to determine the rate at which each ventilation system cleaned down the space. The top-down, highly-diffused air supply system cleaned down to zero detectable particles after 30 minutes, with occasional trace values logged thereafter this was achieved running a single recirculating fan, with the fresh air system disabled. A mobile unit, circulating the same volume of air across the same grade filter, achieved a much slower clean-up rate, achieving a particle volume of around 1,000 per m3 after three hours. These results show a significant improvement in clean-up rates through the use of a top-down, highly diffused air supply. Research carried out using the test cell indicates that 4-5 October 2022. Manchester Central. Register Now! The No.1 Event in the UK for Health Estates, Engineering and Facilities Professionals Healthcare Estates is a unique event that consists of the prestigious IHEEM Annual Conference, Awards Dinner and the UKs largest trade exhibition for the sector. Build innovative and productive partnerships in asset management, integrate efficient patient-centred environments by collaborating with the right people, find inspiration, and foster aspirational attitudes. Visit www.healthcare-estates.com 42 June 2022 www.cibsejournal.com CIBSE June 22 pp40-42, 44 Cleanroom ventilation.indd 42 27/05/2022 16:34