| AIR CLEANING DEVICES GUIDANCE which are relatively inert from a chemical perspective, are simpler to specify. From a ventilation perspective, the guide describes the methods that specifiers can use to translate a manufacturers claims into a robust assessment of performance: The long-term energy implications of any air cleaning device should still be at the forefront of everyones minds Equivalent ventilation rate (eqACH) derived data, the guide provides a method to estimate the CADR from a product data sheet. In simple terms, this metric is used to measure the amount of air treated by a device in terms of the equivalent air changes per hour of clean air. Ventilation should always be the first choice, but in spaces where this is not possible, this metric can be used to assess the ability of a device to clean the air. The relative exposure index (REI) Developed by Benjamin Jones et al,2 the REI is used to highlight types of indoor space, respiratory activity, ventilation provision and other factors that increase likelihood of far-field exposure to SARS-CoV-2. The guide is accompanied by a simple yet powerful spreadsheet tool, which enables specifiers to assess the impact of different interventions on a space, including ventilation, breathing rates and the introduction of an air cleaning device. An example is shown in Figures 3a and 4a. The clean air delivery rate (CADR) The CADR is a commonly used metric that can be useful for comparing devices and for comparing the impact of dilution through ventilation. In the absence of this test-1 per person. Adding an air cleaner that can provide the equivalent of Without air cleaner With air cleaner Room width (m) 7.42 7.42 Room length (m) 7.42 7.42 Room height (m) 2.7 2.7 32 32 Children sitting Children sitting 75 75 25 25 Ls-1 7 7 5 5 of 5Ls-1 per person and an air cleaner ventilation rate of 1ACH; 2.5 2 1.5 1 0.5 0 Ls-1) 1 Ls-1) REI 1.012 Scenarios 0.829 18% per 10Ls-1 Room width (m) 7.42 7.42 Room length (m) 7.42 7.42 Room height (m) 2.7 2.7 32 32 Children sitting Children sitting 75 75 25 25 7 7 5 10 Ls-1 Ls-1 ) 2.5 2 1.5 1 0.5 0 Ls-1 ) REI rates of 5Ls-1 and 10Ls-1 1.012 0.543 46% Scenarios 10Ls-1 5Ls-1 5Ls-1 -1 person to 10Ls-1 60 September 2021 www.cibsejournal.com CIBSE Sep 21 pp58-61 Air cleaning devices.indd 60 27/08/2021 13:01