I'm planning to build a laminar flow hood (LFH) for my mushroom hobby. But I actually also need a fume hood for some tryptamines that I plan to synthesize.

Now it shouldn't be too hard to design a single device that could be used for both, LFH would blow air through a HEPA filter from the front, and a fume hood would reverse the airflow and suck it through the top.

I wouldn't mind that it wasn't just by the flick of a switch, maybe turning the fan around, and connecting it to a different pipe wouldn't be a problem.

So before I start drawing this up myself, I'm wondering whether this has maybe be done before? Somewhere I can find inspiration?

A quick Google search did not yield any results for a current model of this combo of devices. Go for it! And let us know how you did it. I know I'd love something like that myself and am trying to be more handy, so that would be a great project.

One love

Yeah Google didn´t show up much on this side either.

One thing I´m wondering. Maybe squirrel fans are only meant for blowing, not sucking.

I´ll be sure to post my results here.

Hello there.

Just a couple of spontaneous thoughts here.

One thing you'd have to bear in mind is that you don't end up with undesirable toxic components in the filter airflow if you're switching between the two uses. It may be better two have two separate airflow chains connecting to the work area for this reason alone - filtered air in, contaminated air out - and running them at the same time would also be out of the question unless you set it up as a positive pressure glovebox for whatever reason. Would your fume hood include some kind of scrubber function? I'm not convinced a squirrel fan would be happy drawing air through something like that and you'd want to be sure your blower doesn't end up contaminated, as mentioned above.

There are certainly a lot of considerations to take into account, thank you all for you thoughts. And the wrong design could easily result in the device blowing contamination and unwanted particles all over my mushroom project.

But if done properly then I´m convinced this could work out.

Definitely using two airflow channels, LFH is best with air blown from the sides, and the fume hood will be sucking the air in from above.

Regarding the fume hood filter which is usually above could be moved further into the device to prevent dust and other particles to fall from the ceiling once the unit has been switched into LFW mode. That filter could be moved further into the device so falloff wouldn´t be a problem.

I´ll be sure to post results here if this project ever gets realised

I was under the impression that a flow from the back of the LFH allows the clearest means of distinction between 'upflow' and 'downflow' areas while working - although I can see there are potential benefits to working across the flow as well, where of course the distinction rotates to left/right instead. It would, for instance, prevent airborne agents being blown into your face. Is this something you have worked with before?

I do think that you would have to be meticulously careful about your operating procedures and record-keeping if you were to use anything less than two separate fans for a combined system such as you are planning. It sounds like you've put a good deal of thought into this already. I do recall using a built in LFH many moons ago that had an air collecting slot along the front of the work area, which kind of reflects some of your thinking about stowing away the extraction filter.

Looking forward to hearing of your progress on this!