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About this tool
Compute the chimney suction in cubic metres per hour your kitchen needs from its volume, air changes, burners and duct run.
Chimney suction is sized from air changes: airflow in cubic metres per hour equals kitchen volume multiplied by the air changes per hour it needs, which is 10 for light cooking and 15 for daily frying and tempering. This tool applies that, adds capture allowances for the number of burners and for an open-plan layout, then divides by duct efficiency — because the m3/h printed on a chimney is free-air delivery measured with no duct attached, and every metre of pipe and every 90 degree bend takes a slice of it. The output is the rating to shop for and the chimney width that matches your hob.
Open Kitchen Chimney Suction Selector on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Starts from your kitchen's cubic metres and a stated air-change rate you can check.
Shows the percentage the pipe run costs, which is the usual reason a chimney disappoints.
Confirms the chimney is at least as wide as the hob and gives the 65-75 cm installation window.
Work out kitchen volume in cubic metres and multiply by 10 to 15 air changes an hour — use 15 for daily deep frying and tadka. A typical 3.6 x 3 x 3 m kitchen is 32.4 cubic metres, so 15 air changes is 486 m3/h, and with a four-burner hob, a three-metre duct and quiet-running headroom that lands near 1,100 m3/h of rated suction.
For most closed kitchens up to about 35 cubic metres with a short duct, yes. It stops being enough when the kitchen is open plan, the ceiling is high, or the duct runs more than five metres with multiple bends — each bend costs roughly 7% of the flow and each metre about 4%.
Match the width first: a chimney must be at least as wide as the hob, so 60 cm for a 2 or 3 burner and 90 cm for most 4 and 5 burner hobs. More burners running together also need more airflow, which is why the calculation adds about 15% for a four-burner hob over a two-burner one.
65 to 75 cm above the cooktop for most models. Mount it lower and the flame is disturbed and the filter gets hot; mount it higher and the plume spreads before it is captured, so the same suction rating performs worse. Always follow the height stated in the model's manual.
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