Therefore, the volumetric flow rate of clean air required for mycological work is 3.0 sqft x 100 ft/ min = 300 cubic ft / min or 300 CFM. This means that the volume of air flow required in CFM can be determined by multiplying the area of the filter by 100 ft/min.įor example, an 18″ x 24″ filter will have an area of : 1.5ft x 2.0ft = 3.0 sqft. The volume of air that a particular fan can provide at a given static pressure can be shown in a “performance curve” which is usually provided by the manufacturer.įor mushroom cultivation, it is generally suggested that the stream of clean air should flow over the workbench at a speed of 100 feet per minute. As the static pressure increases, the amount of air the fan can produce decreases. These fans are rated based on the volume of air that they produce at zero static pressure in cubic feet per minute (CFM).

Laminar flow hoods typically use a squirrel cage type blower fan that is mounted on top of the hood. They will filter the air just fine, but will not produce laminar flow, and thus won’t work for your flow hood. There are cheaper “HEPA” filters, such as the once available for home furnaces – but don’t get these. NOTE: Make sure you get a proper deep seated filter, such as the ones listed above in order to get smooth laminar flow through the face of the filter. If you want to build a smaller filter, you can choose to get a 12″ x 12″ HEPA filter, which may be adequate- albeit just barely- for small scale home cultivation. Or this 24″ x 24″, by Filtration Group is also good choice. Here is a good one from Amazon, a Novatek filter that measures 24″ x 24″. You are unlikely to find this type of HEPA filter locally, however, there are many sources online, offering a number of different sizes. The information for both the efficiency and the static pressure of the filter should be provided by the manufacturer. This is actually quite a lot of static pressure and requires an adequately sized fan in order to provide a sufficient stream of clean air over your work area. This pre-filter will have a static pressure of 0.1″ to 0.2″, making the total static pressure of the filter system somewhere between 1.0″ and 1.2″. You can use cut-to-fit vent filters to customize the pre-filter to the size you need. It is generally installed at the intake of the blower fan. You will also want to add a pre-filter, which is cheaper and easier to replace than a HEPA and will stop big particles from clogging up your filter. This is simply a measure of the amount of friction between the filter media and the air being pushed through the filter. Most HEPA filters will have between 0.8″ and 1.0″ of static pressure (measured in inches of water). Another consideration when choosing a filter is the static pressure.

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