Extractor fans

[Tealfox]

We have been using smoke machines and mists for some years and always found a fog descending on the audience and the stage. With the news that Covid 19 may be spread by tiny droplets, the need for a silent and efficient extraction system seems to be a priority. Larger, professional theatres have very efficient systems so that when actors smoke on stage it can seen to be whisked away. Does anyone have any experience of installing these? Where is the best place to start?

[J Pearce]

Call a HVAC company, get some quotes, then give them money. It's not really a DIY job even for handy theatre folk.

 

I've had various systems in various venues. The best put the big fan unit and its filters in a plant room then had padded ducting into the theatre space, which kept the noise down to just turbulent air.

The worst had the fan and filters in the theatre roof and could only be run pre/post show and in the interval due to vibration noise - it also had control only from the gantry adjacent to it, so getting to it to turn it and off was a pain.

[Brian]

Larger, professional theatres have very efficient systems...

 

 

I wouldn't go that far. Having spent the last 15 years making lots of smoke in lots of professional venues I'd reckon that fewer than 10% have, what I would call, a good air-handling system.

 

I think the best I came across had the air inlets actually set into the floor, by way of grilles, with extract sited in the ceiling above. That's lots of inlet points and lots of extract points. But as Jon says, this really is a job for the professionals. Trying to work out a DIY system will mean spending money on a system which won't work.

[Jivemaster]

SImple fan you could do yourself BUT it's futile because it will not move enough air evenly enough. Get one or two HVAC companies to quote. Get in while your work is all thy have and the prices may not be too high.

 

Calculating power, air moved, and air speed is part of things, look at heat movement (cost) and air pressure, you will need to push doors against the pressure sometime. Bargain for filter change costs and maybe inline (UV?) air sanitising.

[Dave m]

Generally, high speed extraction is noisy, low speed (high volume) is a lot quieter .I used to work in a 70's built TV studio (budget) and we could only run ventilation between shoots/shots. It sounded like a jet engine and sucked drapes unless you were careful

You can gain a lot by roof openings and airflow.

[adam2]

For a large or complex building I agree that a suitably experienced HVAC contractor should be asked for a quote.

 

DIY is in my view reasonable for a small or simple venue, I did one years ago and AFAIK the installation is still in use. Rather than one or two large extract fans that might produce excessive airflow or be too loud, I installed 16 d0m3stic extract fans. Wired as one circuit of 6 fans and another circuit of 10 fans thereby giving 3 levels of ventilation. Eight fans each side of the building at high level. This was a church hall used for small stage productions, wedding receptions, sunday school, and meetings or lectures of all sorts.

 

Remember that extracted air has to be replaced by fresh air from outside and that this air may need to be heated in cold weather, in the above situation, hot air curtains were installed over external doors total loading was about 20Kw.

 

I stress the need for expert involvement for all but small and simple venues.

Edited July 9, 2020 by adam2

[Tealfox]

Call a HVAC company, get some quotes, then give them money. It's not really a DIY job even for handy theatre folk.

 

I've had various systems in various venues. The best put the big fan unit and its filters in a plant room then had padded ducting into the theatre space, which kept the noise down to just turbulent air.

The worst had the fan and filters in the theatre roof and could only be run pre/post show and in the interval due to vibration noise - it also had control only from the gantry adjacent to it, so getting to it to turn it and off was a pain.

 

 

 

 

Thanks for the advice, I was thinking of using a turnkey supplier.

[mac.calder]

To be perfectly honest, I very much doubt that the volumes air moved by any form of air handling that is not disruptive to the theatre would have a significant effect on droplets expelled by both actors and punters. You need the air to be actively moving hard enough to shift droplets in the right direction - probably towards the floor - that is a huge down draft.

 

Recommendations for indoors revolves more around not recirculating air and filtration over increasing volume. Generally an HVAC system will provide a percentage of fresh air (often called make-up air) and recycle the majority (return air) - this improves efficiency.

 

Your existing air conditioning contractor can probably be engaged to increase the makeup air percentage, and apply filtration across both the makeup and return air. UV C based filtration is probably your best bet - kill the bugs in their tracks.