3 questions about cooker hood extraction rates
The main reason for having a cooker hood is to extract smells and grease from the kitchen. The extraction rate of the cooker hood gives an indication of how powerful the hood is and how effective it is at doing this.
The extraction rate can be called airflow which refers to the amount of air per m3 that can be extracted in one hour. The move powerful the extraction rate the more air can be removed.
1. Is the extraction rate the same for recirculating and ducted hoods?
Short answer no its not.
With all cooker hoods that are used in recirculation mode, as they have no duct to remove the smells and rely on a charcoal filter to do this job, this in turn reduces the airflow by 30%.
If the hood is ducted out then the length and diameter of the duct will affect the extraction rate, the more bends and longer or narrower the duct the lower the extraction rate, if a concertina hose is used this will also affect the extraction rate. If the ducting is longer than 3-4 meter or more and has more than 2 bends this will reduce the extraction rate of the appliance.
Recommended size manufactures is rigid 150mm diameter ducting for optimum results.
2.What extraction rate do I need?
In order to calculate what extraction rate / airflow hood you need, you need to you simply measure the length, width and height of you room and multiply them together then multiply by 10, please see example below.
For example: If your kitchen is 5 meters wide, 7 meters long and 3 meters high, your calculation will be:
(5 x 7 x 3) x 10 = 1050
This means that a hood with an extraction rate of 1050 m3/h should achieve efficient ventilation of the room, anything less will not extract air effectively.
3. How is the extraction rate reported?
Most manufacturers, comply with the European standard IEC EN 61591. This means that the airflow is measured in a realistic scenario: after one meter of ducting plus one 90° bend plus one more meter of ducting.
If a hood can only be used in recirculation mode, then the airflow should be measured at the point of the metal grease filter with the charcoal filter in place (which reduces the airflow.
At Appliance Spares Direct we can help you order the correct hood and also ducting needed for you.