【正文】 alyser for subsequent analysis shall be provided. The recording interval shall be 2 s or less. Test conditions The background concentration of tracer gas in the test room shall not exceed 108 volume fraction. EN 141753:2022 10 Licensed copy:PONTYPRIDD COLLEGE, 06/03/2022, Uncontrolled Copy, 169。 BSI Positioning of test equipment for inner measurement plane Nine sampling probes (see ) shall be arranged in a grid formed by the intersection of lines as follows: a) three equally spaced lines in the vertical direction. The space between the lines shall be (100 + 5) mm. b) three equally spaced lines in the horizontal direction. The space between the lines shall be (100 + 5) mm. The test gas injector (see ) shall be arranged with its centre inline and (150 + 5) mm from the centre of the sampling probe grid. The sampling probe grid shall be positioned together with the injector so that the sampling probes are on the inner measurement plane and the injector is in the workspace of the fume cupboard on a plane (150 + 5) mm from the inner measurement plane. Figure 1 and Figure 2 show examples of the positioning of the inner measurement plane for different designs of fume cupboards. Key 1 inner measurement plane 2 test sash opening Figure 1 — Inner measurement plane EN 141753:2022 11 Licensed copy:PONTYPRIDD COLLEGE, 06/03/2022, Uncontrolled Copy, 169。 BSI Key 1 sash plane 6 inner measurement 2 horizontal sashes 7 lower reference point 3 sash frame 8 airfoil 4 handle or airfoil 9 work surface 5 upper reference point 10 test sash opening Figure 2 — Example for exact positioning The sampling probe grid shall be positioned on the inner measurement plane with its centre probe at points formed by the intersection of lines as follows: c) a series of equally spaced lines between the vertical side boundaries of the inner measurement plane with the two outermost lines (130 + 5) mm from the vertical side boundaries. Any lines in between shall be at a distance of 600 mm or less from the outermost lines and to each other. d) a series of equally spaced lines between the horizontal boundaries of the inner measurement plane with the two outermost lines (130 + 5) mm from the horizontal boundaries. Any lines in between shall be at a distance of 600 mm or less from the outermost lines and to each other. Positioning of test equipment for outer measurement plane Injector grid Nine test gas injectors shall be arranged inside the workspace of the fume cupboard on a plane (200 + 5) mm away from the plane of sash. They shall be positioned with horizontal axis, the test gas flow direction towards the sash and in a grid formed by the intersection of the following lines: a) three equally spaced vertical lines between the two extreme side boundaries of the sash opening with the two outermost lines (100 + 5) mm from the two extreme side boundaries. b) three horizontal lines with the bottom line (100 + 5) mm, the middle line (250 + 5) mm and the top line (650 + 5) mm above the bottom horizontal boundary of the sash opening. EN 141753:2022 12 Licensed copy:PONTYPRIDD COLLEGE, 06/03/2022, Uncontrolled Copy, 169。 BSI Sampling probe grid The sampling probes (see ) shall be positioned at grid points formed by the intersection of lines on the outer measurement plane as follows: a) a series of equally spaced vertical lines between the side boundaries of the outer measurement plane with the two outermost lines on the side boundaries. Any lines inbetween shall be at a distance of 400 mm or less from the outermost lines and from each other. b) a series of horizontal lines between the horizontal boundaries of the outer measurement plane with the two outermost lines on the horizontal boundaries and the penultimate lines (200 + 5) mm from the horizontal boundaries. Any lines in between shall be equally spaced at a distance of 200 mm or less for vertical sashes respectively 400 mm or less for horizontal sashes from the penultimate lines and from each other. Figure 3 shows examples of the positioning of the outer measurement plane for four different designs of fume cupboards. Key 1 outer measurement plane 2 test sash opening Figure 3 — Outer measurement plane Where the plane of the sash does not meet the work surface, the lowest row of sampling probes shall be positioned (50 177。 5) mm in front of the vertical plane through the front edge of the work surface. If the handle of the sash is such that it prevents the movement of the sash with the sampling probes in this position, the sampling probes shall be placed further away but as close as possible to the outer measurement plane. The position of each sampling probe shall be recorded in the test report. When low level fume cupboards or walkin fume cupboards are tested, the test report shall record the height of positioning of the injector grid and the sample grid. When the test opening exceeds 1000 mm, the distance between horizontal lines [see b)] may be 400 mm instead of 200 mm. Test procedure Preparation Switch on all supply and extract air systems and adjust controls to give specified flow rates. Connect the cylinder of test gas to the test gas flow regulator and to the test gas injector(s). Connect the sampling probes to the collecting and analysing system. Switch on suction pumps, the gas analyser and the data recording/storage system and allow ample time for the instruments to stabilise. EN 141753:2022 13 Licensed copy:PONTY